Roofing Glossary

Glossary of Roofing Terms

ARCA Roofing Industry Glossary

Extracted and scrubbed (with permission) from National Roofing Contractors Association


Onecomponent of a two-component polymer system; for polyurethane foamand coatings, the isocyanate component. Seealso isocyanate and methylene diphenyl diisocynate (MDI)


Theability to resist being worn away by contact with another moving,abrasive surface, such as foot traffic, mechanical equipment,wind-blown particles, tree limbs, etc.


Theability of a material to accept within its body quantities of gasesor liquid, such as moisture.


Theexposure of a specimen to a specified test environment for aspecified time with the intent of producing in a shorter timeperiod effects similar to actual weathering.


Aliquid coating system based on acrylic binders dispersed in water(occasionally in solvents) with pigments and several proprietaryadditives that cures by coalescence and air drying.


Polymersof acrylic or methacrylic monomers, often used as a latex base forcoating systems.

Activemetal (anodic)

Ametal or material that readily gives up electrons to a cathodic(noble) material. (See anodic) An active metal will corrode inthe presence of moisture when in contact with a cathodic metal.


Tocause two surfaces to be held together by the combined strength ofthe molecular forces and the mechanical interlock- ingachieved between adhesive and the bonded surface. See adhesion,adhesive and bond


(1)The degree of attachment between two surfaces held together byinterfacial forces—mechanical or chemical or both; (2)the degree of attachment or bonding between application of the samesubstance; (3) the combined ultimate strength ofthe molecular forces and the mechanical interlocking achieved betweenthe adhesive and the surface bonded. Adhe- sionis measured in shear and peel modes.


Acementing substance that produces a steady and firm attachment oradhesion between two surfaces.

Adhesivebond break

Amaterial to facilitate independent movement between two units thatwould otherwise bond together.


AssociatedGeneral Contractors of America.


Thermalresistance value established by using artificial conditioningprocedures for a prescribed time period. See “Long- termthermal resistance (LTTR).”


(1)Crushed stone, crushed slag, water-worn gravel used for surfacing abuilt-up roof system; (2) any granular mineral material.

Aggregate,lightweight (LWA)

Aggregateof low density; examples include coal bottom ash, pumice, scoria,volcanic cinders, tuff and diatomite; expand- edor sintered clay, shale, slate, diatomaceous shale, perlite,vermiculite or slag and bonded or sintered coal combustion products(CCPs) used to produce lightweight concrete or component products.


(1)The effect on materials of exposure to an environment for an intervalof time; (2) the process of exposing materials to anenvironment for an interval of time.


AmericanInstitute of Architects.


Theassembly of materials used in building construction to reduce orretard the uncontrolled passage of air into and out of thebuilding.


Airleakage into the building.


Theunintended movement of air from a location where it is intended to becontained to another location.


Acavity or unfilled space between two constituent parts in a roofassembly or other enclosure element of a building.


Anorganic polymer containing straight or branched chain arrangements ofcarbon atoms. As compared to aromatic ure- thanes,coatings based on aliphatic urethane binders typically have betterweathering characteristics.

Aliphaticpolyurethane coating

Apolyurethane coating that contains a specific class of isocyanatesbased on a long straight chain molecular structure. Normallyused in finish coats that are exposed to the elements. It is notedfor its good weather resistance.


Thecapacity of water solutions to neutralize acids; a property impartedby the solution’s content of carbonates, bicarbon- ates,hydroxides, and occasionally borates, silicates, and phosphates.


Crackingof a surfacing bitumen, asphalt, coating or mastic or coating on aspray polyurethane foam (SPF) roof system thatoccurs during the aging process in which the loss of volatile oilsand the oxidation brought about by solar radiation producesa pattern or cracks similar to an alligator’s hide; the cracks mayor may not extend through the surfacing materi- al.


Sheetsteel with a thin aluminum coating bonded to the surface to enhanceweathering characteristics.


Anonrusting, malleable metal sometimes used for metal roofing andflashing.


Thetemperature of the air existing on all sides; air temperature.


(1)The determination of the nature or proportion of one or moreconstituents of a substance, whether separated or not; (2)a qualitative or quantitative determination of one or more componentsof a sample cut from an existing roof system.


Ametal or material that readily gives up electrons to a cathodicmaterial in the presence of an electrolyte (see “galvanic cell,”galvanic series and cathodic). As a result, the anodic materialoxidizes to protect the cathodic material from corro- sion.


AmericanNational Standards Institute.


(Formerly)American Plywood Association. The full designation in current use is“APA—The Engineered Wood Associa- tion.”


(Formerly)American Plastics Council. The full designation in current use is“The Plastics Division of the American Chem- istryCouncil (ACC).” “ACC Plastics Division” is the common-use form.


(Formerly)American Plastics Council/Spray Polyurethane Foam Alliance. See APC


Seeatactic polypropylene


Theaverage quantity (mass, volume or thickness) of material applied perunit area.


Thetemperature of a material, such as hot asphalt, when applied to theroof.

Apronflashing (Includes illustration)

A term used for a flashing located at the juncture of the top ofa sloped roof and a vertical wall, chimney or steeper-sloped roof.


Aperson technically qualified and professionally licensed to practicearchitecture; that is, designing and administering the constructionof buildings.


Ametal roof panel; usually requires solid decking underneath andrelies on slope to shed water.


See“dimensional shingle.”


Araised, flashed assembly, typically a single- or double-wood memberattached to a wood base plate, that is anchored to thedeck. It is used to accommodate thermal stresses in a waterproofingsystem where an expansion joint is not requires orto separate large roof areas or roof systems composed ofdifferent/incompatible materials, it may be used to facilitate installationof tapered insulation.


Designor application techniques particular to a specific geographicalregion.


AsphaltRoofing Manufacturers Association.


Anorganic polymer usually containing one or more benzene ringstructures. As compared to aliphatic, coatings based on aromaticpolyurethane is usually have tougher physical properties.


Agroup of natural, fibrous impure silicate materials.




AmericanSociety of Civil Engineering.


AmericanSociety of Home Inspectors.


AmericanSociety of Heating, Refrigerating and Air-Conditioning Engineers.


Adark brown to black cementitious material in which the predominatingconstituents are bitumens found in a natural stateor more commonly left as a residue after evaporating or otherwiseprocessing crude oil or petroleum. See bitumen Asphaltmay be further refined to conform to various roofing gradespecifications:” “””asphalt, dead-level: Roofing asphalt conformingto the requirements of ASTM D312, Type I.” “ “””asphalt,flat: Roofing asphalt conforming to the requirements ofASTM D312, Type II. “ “ “””asphalt, steep: Roofing asphaltconforming to the requirements of ASTM D312, Type III. “ “ “””asphalt,special steep: Roofing asphalt conforming to the requirements of ASTMD312, Type IV. “ “ asphalt, waterproof- ing:A waterproofing asphalt conforming to the requirements of ASTM D449,Types I, II and III.”

Asphaltcore board

Anasphaltic panel that may be used as a cover board layer beneathbuilt-up and polymer-modified bitumen roof mem- branes.It is a semi-rigid, multi-ply panel constructed of a core ofwater-insoluble mineral filler with bituminous binder sandwichedbetween two reinforcing facings.


Amixture of asphalt particles and emulsifying agent, such as bentoniteclay or soap, and water.


Anasphalt-saturated and/or asphalt-coated felt. See felt



Asphaltroof cement

Atrowelable mixture of solvent-based bitumen, mineral stabilizers,other fibers and/or fillers. It can be classified accord- ingto two available standards: ASTM D2822, applicable toasbestos-containing materials and ASTM D4586, applicable to asbestos-freematerials. Both standards contain provisions for Type I and Type IImaterials.” Type I is sometimes referred toas “plastic cement” and is made from asphalt characterized asself-sealing, adhesive and ductile and conforming to ASTMD312, Type I; ASTM D449, Type I or Type II; or ASTM D946. See plasticcement and flashing cement” “ Type II is generallyreferred to as “vertical-grade flashing cement” and is made fromasphalt characterized by a high softening point andrelatively low ductility and conforming to the requirements of ASTMD312, Type II or Type III; or ASTM D449, Type III. Seeplastic cement and flashing cement”


Ashingle manufactured by coating a reinforcing material (paper felt orfiberglass mat) with an asphalt-based coating and havingmineral granules on the side exposed to the weather. See shingle


Asphaltproduced by blowing air through molten asphalt at an elevatedtemperature to raise its softening point and modify otherproperties.


Thefull designation in current use of the largest voluntary standardsdevelopment organizations in the world formerly knownas the American Society for Testing and Materials.


High-molecular-weightpolymer formed by the polymerization of propylene and characterizedby random arrangement of theside methyl groups around the chain backbone.


Discolorationthat may occur because of atmospheric contaminants such assulfur-containing gases.


Thecavity or open space above the ceiling and immediately under the roofdeck of a steep-slope roof.


AmericanWood Protection Association; formerly American Wood-PreserversAssociation.


Onecomponent of a two-component polymer system; for polyurethane foamand coatings, the resin component.


Thepractice of nailing the concealed portion of a roofing ply, steeproofing unit or other components in a manner such thatthe fasteners are covered by the next ply, or course, and are notexposed to the weather in the finished roof system. Hot-moppedroofing felts and polymer-modified bitumen sheets may be backnailedto prevent slippage. Also referred to as“blindnailing.”


Rollinga coating by hand, normally behind the spray or power rollerapplicator, to ensure better coverage and adhesion.


Arigid plate to support an end lap to provide uniform compression.


Amaterial, such as minimum nominal #1-1/2 inch size or #4, oralternatively, #3, #24, #2 or #1—as specified in ASTM D448—smoothriver stone, crushed stone, standard precast concrete pavers orinterlocking, beveled, doweled or con- touredfit lightweight concrete pavers, that employs its mass and the forceof gravity to hold a roof membrane system in place.


Seesteel joist


Abuilding profile featuring a rounded profile to the roof on the shortaxis but with no angle change on a cut along the long axis.


Thefirst coat of a multicoat system.

Baseflashing (membrane base flashing)

Pliesor strips of roof membrane material used to closeoff and/or seal aroof at the horizontal-to-vertical intersections, suchas at a roof-to-wall juncture. Membrane base flashing covers the edgeof the field membrane and extends up the verticalsurface. See flashing


Thebottom or first ply in a built-up or polymer- modified bitumen roofor waterproofing system when additional plies are tobe subsequently installed.


Animpregnated, saturated or coated felt placed as the first ply in somelow-slope roof and waterproofing systems.

Basicwind speed

Threesecond gust wind speed in miles per hour at 33 feet above ground inExposure C as defined in the latest edition of theAmerican Society of Civil Engineers standard ASCE 7, “MinimumDesign Loads for Buildings and Other Structures.”


(1)Cap or cover; (2) in a metal roof, a metal closure set over, orcovering the joint between, adjacent metal panels; (3) in a steep-sloperoof system, a strip of wood or metal usually set in or over thestructural deck, used to elevate and/or attach aprimary roof covering; (4) in a single-ply membrane roof system, anarrow plastic or metal bar that is used to fasten or holdthe roof membrane and/or base flashing in place.


Aname applied to a common standing seam metal panel profile that mayuse a square- or rectangular-profile snap-on cap ormay be attached to and formed around a beveled wood or metal batten.


Aprimary member, usually horizontal, that is subjected to bendingloads. There are three types: simple, continuous and cantilever.


(1)A plate used to distribute fastener load in metal panel roof systemsplaced over rigid board insulation and through-fas- tenedto the roof deck; (2) a steel plate that is set on the top of amasonry support on which a beam or purlin can rest.


Aporous clay formed by the decomposition of volcanic ash that swellsfive to six times its original volume in the presence ofwater.


Ametal panel profile featuring a step-down profile that runsperpendicular to the slope of the roof; has a shingled appear- anceand is water-shedding.


(1)A class of amorphous, black or dark-colored, (solid, semi-solid orviscous) cementitious substances, natural or manu- factured,principally composed of high-molecular-weight hydrocarbons, solublein carbon disulfide, and found in asphalts, tars,pitches and asphaltites; (2) a generic term used to denote anymaterial composed principally of bitumen, typically asphaltor coal tar.


Containingor treated with bitumen, e.g., bituminous concrete, bituminous feltsand fabrics, and bituminous pavement.


(1)See asphalt emulsion; (2) a suspension of minute globules ofbituminous material in water or in an aqueous solution; (3)a suspension of minute globules of water or of an aqueous solution ina liquid bituminous material (invert emulsion).


Awaterproofing method available for positive-side waterproofing only;cold or hot bituminous application with reinforcing material.


Atheoretical, perfect emitter and absorber of thermal radiation. Itemits radiant energy at each wavelength at the maxi- mumrate possible for its temperature and absorbs all incident radiation.


Fiberglassor other compressible fibrous insulation, generally available in rollform.

Blastfurnace slag

Thenonmetallic product, consisting essentially of silicates andalumino-silicates of calcium and other bases, that is devel- opedin a molten condition simultaneously with iron in a blast furnace.


(1)A raised portion of a roofing membrane resulting from local internalpressure, such as an enclosed pocket of air, which maybe mixed with water or solvent vapor, trapped between impermeablelayers of felt or membrane or between the membraneand substrate; (2) the similarly formed surface swelling in coatedprepared roofing such as asphalt shingles; (3)separation of a coating from a substrate; may be caused by waterabsorption and the resultant swelling or subsurface corrosion.


Theformation in the film of dome-shaped, liquid or gas-filledprojections resulting from local loss of adhesion and lifting ofthe film from the substrate or previously applied coating.


(1)Sections of wood (which may be preservative-treated) built into aroof or waterproofing assembly, usually attached abovethe deck and below the membrane or flashing, used to stiffen the deckaround an opening, act as a stop for insu- lation,support a curb, or serve as a nailer for attachment of the membraneand/or flashing; (2) wood cross-members installedbetween rafters or joists to provide support at cross-joints betweendeck panels.


Anexpanding agent used to produce a gas by chemical or thermal actionor both in manufacture of hollow or cellular materials.


(1)The adhesive and/or cohesive forces holding two components inpositive contact; (2) a surety; typical types are: bid, performanceand payment; (3) a guarantee relating to roof system performance.


Achemical substance applied to a suitable substrate to create bondbetween it and a succeeding layer. See adhesive


(1)A covering made of flexible material that may be preformed to aparticular shape, used to exclude dust, dirt, moisture, etc.,from around a penetration; (2) a flexible material used to form aclosure, sometimes installed at inside and outside corners.


Structuralelements installed to provide restraint or support or both to othermembers so the complete assembly forms a stablestructure; may consist of knee braces, cables, rods, struts, ties,shores, diaphragms, rigid frames, etc.


(1)An instance of a membrane or base flashing unsupported at a juncture;(2) occurs in steep-slope roofing when the nestingmethod is not used in re-covering, such as roofing over standard-sizeasphalt shingles with metric-size asphalt shingles.

Britishthermal unit (Btu)

Theheat energy required to raise the temperature of one pound of waterone degree Fahrenheit.


Tocast or distribute granular or aggregate surfacing material.


Embeddinga ply or membrane by using a broom or squeegee to smooth it out andensure contact with the adhesive under theply or membrane.


SeeBritish thermal unit


Asheet (membrane, felt, etc.) lap facing upslope allowing water to hitagainst the edge of it rather than facing downslope toallow water to run over it smoothly.


Anupward, elongated displacement of a roof membrane frequentlyoccurring over insulation or deck joints. A buckle may bean indication of movement within the roof assembly.


Theminimum construction requirements established generally by nationalorganizations and adopted completely or in alteredform by local governing authorities. Building code controls design,construction, quality of materials, use and occu- pancy,location, and maintenance of buildings and structures within the areafor which the code was adopted.


Exteriorof a building.

Built-uproof (BUR)

Acontinuous, semi-flexible roof membrane consisting of multiple pliesof saturated felts, coated felts, fabrics or mats as- sembledin place with alternate layers of bitumen and surfaced with mineralaggregate, bituminous materials, a liquid-ap- pliedcoating or a granule-surfaced cap sheet.


Thelower, exposed edge of a shingle, tile or shake.


Ajoint formed by adjacent, separate sections of material, such aswhere two neighboring pieces of insulation abut.


Aprocess of indenting two or more thicknesses of metal that arepressed against each other to prevent slippage between themetal.


Asynthetic elastomer based on isobutylene and a minor amount ofisoprene. It can be vulcanized and features low permeabilityto gases and water vapor. Butyl rubber is manufactured into varioussheet goods, blended with other rubber materials,and is often used to make sealant.


Asealant tape sometimes used between metal roof panel seams and/or endlaps; also used to seal other types of sheet metaljoints and in various sealant applications.


Astructural framing member.


Amanufacturing process by which some polymeric membranes and othersheetings are produced.


See“no-cut valley.”


Aslight convexity, arching or curvature (as of a beam, roof deck orroad).


Abeveled strip used to modify the angle at the point where the roofingor waterproofing membrane meets any vertical element.


(1)Usually composed of metal, used to cover or shield the upper edges ofthe membrane base flashing or wall flashing; (2)a flashing used to cover the top of various buildings components,such as parapets or columns. See flashing and cop- ing


Asheet, often granule-surfaced, used as the top ply of some built-upor polymer-modified bitumen roof membranes and/ orflashings.


(1)The action by which the surface of a liquid where it is in contactwith a solid is elevated or depressed depending on the relativeattraction of the molecules of the liquid for each other and forthose of the solid; (2) the siphoning of liquid into a jointor void between two adjacent surfaces.


Aningredient that initiates a chemical reaction or increases the rateof a chemical reaction when combined with another chemical.


Ametal or material that readily attracts electrons from an anodicmaterial in the presence of an electrolyte. See galvanic series


Acomposition of vehicle and pigment used at ambient temperatures forfilling/sealing joints or junctures; remains elastic foran extended period of time after application.


(1)The physical process of sealing a joint or juncture; (2) sealing andmaking weathertight the joints, seams or voids be- tweenadjacent surfaces by filling with a sealant.


Theformation of a partial vacuum or cavity in a liquid.


Apoured-in-place roof deck material composed of Portland cement,water, a foaming agent or pregenerated foam and air. It’soven-dry density is about 24 to 32 pounds per cubic foot.

Cellularglass insulation

Arigid closed-cell insulation board made from crushed glass andhydrogen sulfide gas.


Heavycement-based compounds and various additives that are mixed andpackaged for use in a dry form; the packaged mixtureis then mixed with water and liquid bonding agents to a workableconcrete-like consistency.

Cementitious-woodfiber deck

Treatedwood fibers bonded together with Portland cement or other resinous-or cementitious-type binder that are compressedand molded to form a structural material. Examples of product tradenames are Tectum and Insul-rock.


Ametric unit of measurement equal to one-hundredth (0.01) of a meter,or 0.393 inches.

Centipoise(cP or cPs)

Aunit of measure of dynamic viscosity in the centimeter-gram-secondsystem of units equal to one one-hundredth of apoise (1 P = 100 cP = 1 g•cm-1•s-1). (The viscosity of water at70 F is one centipoise. The lower the number, the less viscousthe material.)


Aunit of kinematic viscosity in the centimeter-gram-second system ofunits equal to one one-hundredth of a stokes (1 St =100 cSt = 1 cm2•s-1); the ratio of a liquid’s dynamic viscosityto its density.


Apowdery residue on the surface of a material.


Theformation of a friable powder on the surface caused by thedisintegration of the binding medium by weather factors.


Insteep-slope roof construction, a type of flashing used atroof-to-wall junctures and other roof-to-vertical plane intersec- tionswhere an internal gutter is needed to handle runoff. Commonly usedwith profile tile.


Incoatings, slight breaks in the film that do not penetrate to thepreviously applied coating or substrate; also termed “weatherchecking.”


Theability to withstand contact with specified chemicals without asignificant change in properties.


Stone,masonry, prefabricated metal or wood-framed structure containing oneor more flues projecting through and above aroof.

Chlorinatedpolyethylene (CPE)

Athermoplastic material used for single-ply roof membranes composed ofhigh-molecular-weight polyethylene that has beenchlorinated with a process that yields a flexible rubber-likematerial. CPE can be vulcanized but usually is used in a nonvulcanizedstate.

Chlorosulfonatedpolyethylene (CSPE or CSM)

Probablybest known by the DuPont trade name Hypalon,® a synthetic,rubber-like thermoset material, based on high-mo- lecular-weightpolyethylene with sulphonyl chloride, usually formulated to produce aself-vulcanizing membrane. Mem- branesin vulcanized and nonvulcanized forms are used; classified by ASTMD5019.


(1)A principal member of a truss, which extends from one end to theother, primarily to resist bending; (2) the straight line betweentwo points on a curve; (3) the span of an arch.


Amaterial used as the exterior wall enclosure of a building.


Acontinuous metal strip, or angled piece, used to secure metalcomponents. See clip


(1)An upward extension of enclosed space created by carrying a setbackvertical wall (typically glazed) up and through theroof slope; (2) two intersecting shed roofs on different planes.


Anoncontinuous metal component or angle piece used to secure a metalpanel to a substrate or two or more metal com- ponentstogether. See cleat

Closed-cutvalley (Includes illustration)

A method of valley application in which shingles from oneside of the valley extend across the valley while shingles from theother side are trimmed back approximately 2 inches fromthe valley centerline.


Adark brown- to black-colored, semisolid hydrocarbon produced by thedistillation of coal. Coal-tar pitch is further refined toconform to the following roofing grade specifications: coal-tarpitch: A coal tar used as the waterproofing agent in dead-levelor low-slope built-up roof membranes and membrane waterproofingsystems, conforming to ASTM D450, Type I.coal-tar roof cement: A trowelable mixture of processed coal-tarbase, solvents, mineral fillers and/or fibers. Classified byASTM D4022, “”Coal Tar Roof Cement, AsbestosContaining.””coal-tar waterproofing pitch: A coal tar used as thedamp- proofingor waterproofing agent in below-grade structures, conforming to ASTMD450, Type II. “* ### Coarse orange-peel surfacetexture In spray polyurethane foam (SPF) roofing, a surface showing atexture where nodules and valleys are ap- proximatelythe same size and shape. This surface is acceptable for receiving aprotective coating because of the round- nessof the nodules and valleys.

Coatedbase sheet

Acoated felt intended to be used as a base ply in a built-up orpolymer-modified bitumen roof membrane.

Coatedfelt (sheet)

(1)An asphalt felt that has been coated on both sides with harder, moreviscous asphalt; (2) a fiberglass felt that has been simultaneouslyimpregnated and coated with asphalt on both sides.


(1)A layer of liquid material applied to a surface for protection orappearance; (2) A fluid material applied in the field as a filmto the roof surface to provide weather protection to the originalroof substrate.(3) a factory- or field-applied protective ordecorative layer bonded to its substrate such as a metallic coatingdeposited mechanically, by hot dipping or electro- plating,or a cured paint system application on sheet metal or buildingsurface, or anodized finish on aluminum.


Acollection of laws (regulations, ordinances or statutoryrequirements) adopted by an authority having jurisdiction. See buildingcode and “model (building) code.”

Coefficientof thermal expansion

Thecoefficient of change in dimension of a material per unit ofdimension per degree change in temperature.


Theapplication of a finish to a coil of metal using a continuousmechanical coating process.


Theprocess of shaping metal into desired profiles without theapplication of heat.


Ajoint formed when a concrete surface hardens before the next batch ofconcrete is placed against it; characterized by a poorbond unless special procedures are observed.>


Theprocess of forming steel into sheets, panels or shapes on a series ofrollers at room temperature.


Designedfor or capable of being applied without heating as contrasted tohot-applied. Cold-applied materials are fur- nishedin liquid state, whereas hot-applied materials are furnished assolids that must be heated to liquefy before applica- tion.


Ametal cap flashing around a vent pipe projecting above a roof deck.


Themeasurement of performance for paint systems testing the ability toresist fading.


Theability of a material to retain its original color after exposure toweather.


Instructures, a relatively long, slender structural compression membersuch as a post, pillar or strut; usually vertical with thecompression load acting in (or near) the direction of itslongitudinal axis.


Aterm used to describe an installation of finishing slate shingles orwood roofing at the ridge of a roof whereby the shin- gleson one side project beyond to the apex of the ridge.


Capableof burning.


Anact or instance of burning.


Twoor more substances that can be mixed, blended or attached withoutseparating, reacting or affecting the materials adversely.

Compositeboard roof insulation

Rigidboard insulation generally composted of perlite or wood fiberboardfactory- bonded to polyisocyanurate or polysty- rene.


Inpolymer processing and applications, an intimate admixture ofpolymer(s) with all the materials necessary for the prop- ertiesrequired of the finished product.


(1)Subjecting a material to a load that will tend to compress or pushthe material together; (2) a decrease in length pro- ducedon a test specimen during a creep test.


Theproperty of a material that relates to its ability to resistcompression loads.


Seesplice plate


Theliquid resulting from the condensation of a gas.


Theconversion of water vapor or other gas to liquid phase as thetemperature drops or atmospheric pressure rises; the actor process of condensing. See dew point


Tomake denser or more compact, as when a material (e.g., water vapor)changes from its gas phase to its liquid phase.


Thestorage of a material specimen under specified temperature, humidity,etc., for a specified time prior to testing.

Conductance,thermal (C)

Thethermal transmission in unit time through unit area of a particularbody or assembly having defined surfaces, when unitaverage temperature difference is established between the surfaces.C=Btu/h•ft2•F.


Ameasure of the ability of a material to conduct electrical current;the reciprocal of electric resistance.

Conductivity,thermal (k)

Seethermal conductivity (k)




Anenlargement or catch basin at the top of a downspout or leader toreceive rainwater from a gutter or scupper.


Theprocess of making a material or surface unclean or unsuited for itsintended purpose, usually by the addition or at- tachmentof undesirable foreign substances.


Agroove that is formed, sawed or tooled in a concrete or masonrystructure to regulate the location and amount of crackingand separation resulting from the dimensional change of differentparts of the structure, thereby avoiding the develop- mentof high stresses.


Aroof system that uses products made of highly reflective and emissivematerials for its top surface. Cool roof surfaces canremain at markedly lower temperatures when exposed to solar heat inservice than surfaces of roofs constructed with traditionalnon-reflective roofing products.


Thecovering piece on top of a wall exposed to the weather, usually madeof metal, masonry or stone.


Asoft, malleable, naturally weathering metal used in metal roofing orflashing.


Thedecorative horizontal molding or projected roof overhang.


Verticalwood or metal strips installed on steep-slope roofs over whichhorizontal battens are secured. The primary roof coveringis attached or secured to these horizontal battens.

Counterflashing(Includes illustration)

Formed metal or elastomeric sheeting secured on or into awall, curb, pipe, rooftop unit or other surface to cover and protectthe upper edge of a base flashing and its associated fasteners.


(1)The term used for a row of roofing material that forms the roofing,waterproofing or flashing system; (2) one layer of a seriesof materials applied to a surface (e.g., a five-course wall flashingis composed of three applications of roof cement withone ply of felt or fabric sandwiched between two layers of roofcement).


Aninsulation board used over closed cell plastic foam insulation (e.g.,polyisocyanurate) to prevent blistering when used inconjunction with hot bituminous membranes. Suitable cover-boardinsulations are glass-faced siliconized gypsum board,fiberglass board, perlite board, wood fiberboard or mineralfiberboard. Cover boards are also recommended be- tweenpolyisocyanurate insulation and single-ply membranes to protect thepolyisocyanurate.


Ametal strip sometimes installed over or under the joint betweenformed metal pieces.


Thesurface area uniformly covered by a specific quantity of a particularmaterial at a specific thickness.




Anonlinear separation or fracture occurring in a material.


Incoatings, visible breaks in the film thickness that extend to thesurface and the previously applied coating or substrate.


Fine,random cracks forming a network on the surface of a membrane, coatingor film.


Timein seconds (at a given temperature) when the A and B components ofpolyurethane foam will begin to expand after beingmixed; recognizable as a change in color of the materials.


Thetime-dependent part of a strain resulting from stress.

Cricket(Includes illustration)

A relatively small area of a roof constructed to divert water froma horizontal intersection of the roof with a chimney, wall, expansionjoint or other projection.


ColdRegions Research and Engineering Laboratory.


Theproduct resulting from the artificial crushing of rocks, boulders orlarge cobblestones, substantially all faces of which haveresulted from the crushing operation.


Acompound of cement, quartz or silica sand and other active chemicalsthat are mixed and packaged for use in a dry powderform. The packaged mixture is then mixed with water and applied to aconcrete surface where it penetrates into thepores of concrete.


ConstructionSpecifications Institute.


Seechlorosulfonated polyethylene


(1)A raised member used to support roof penetrations, such as skylights,mechanical equipment, hatches, etc., above the levelof the roof surface; (2) a raised roof perimeter relatively low inheight.


Aprocess whereby a material is caused to form permanent molecularlinkages by exposure to chemicals, heat, pressure and/orweathering.


Thetime required for a material to reach its desirable long-termphysical characteristics.


Concretethat has attained its intended design performance properties.


Anadditive in a coating or adhesive that results in increased chemicalactivity between the components with an increase ordecrease in rate of cure.


Solvent-thinnedbitumen used in cold-process roof adhesives, roof cements and roofcoatings.


Apermanent detail designed to prevent lateral water movement in aninsulation system and used to isolate sections of a roofsystem. (A cutoff is different from a tie-in, which may be atemporary or permanent seal.) See tie-in


Theopen portions of a strip shingle between the tabs; sometimes referredto as a keyway.


Treatmentof a surface or structure to resist the passage of water in theabsence of hydrostatic pressure.


Absolutelyhorizontal or zero slope. See slope


Theweight of a structure itself, including the weight of fixtures orequipment permanently attached to it.


Seeasphalt, dead-level


Astructural component of the roof of a building. The deck must becapable of safely supporting the design dead and live loads,including the weight of the roof system, and the additional liveloads required by the governing building codes and providethe substrate to which the roof or waterproofing system is applied.Decks are either noncombustible, (e.g., corru- gatedmetal, concrete or gypsum) or combustible (e.g., wood plank orplywood).

Deflection(bowing, sagging)

(1)The deformation of a structural member as a result of loads acting onit; (2) any displacement in a body from its static positionor from an established direction or plane as a result of forcesacting on the body.


Anychange of form, shape or dimensions produced in a body by a stress orforce, without a breach of the continuity of its part.


Adeleterious change in the chemical structure, physical properties orappearance of a material from natural or artificial exposure(e.g., exposure to radiation, moisture, heat, freezing, wind, ozoneand oxygen).


Separationof the laminated layers of a component or system.

Dewpoint temperature

Thetemperature at which air becomes saturated with water vapor; thetemperature at which air has a relative humidity of 100percent.


Seedry film thickness


Afloor slab, metal wall panel, roof panel or the like having asufficiently large in-plane shear stiffness and sufficient strengthto transmit horizontal forces to resisting systems.


Inroofing and waterproofing, dimensional changes in dissimilarinterfacing materials characterized by different and incompatiblerates of change of dimensions, such as membranes and flashingmaterials, resulting from a temperature changeor change in loading. See thermal movement


(1)The movement of water vapor from regions of high concentration (highwater vapor pressure) toward regions of lower concentration;(2) spreading of a constituent in a gas, liquid or solid tending tomake the composition of all parts uniform; (3)the spontaneous movement of atoms or molecules to new sites within amaterial.


Thedegree to which a material maintains its original dimensions whensubjected to changes in temperature and humidity.


U.S.Department of Energy.

Dormer(Includes illustration)

A structure projecting from a sloping roof usually housing awindow or ventilating louver.


Applicationof asphalt, slate or wood roofing such that the lapped portion is atleast 2 inches wider than the exposed por- tion,resulting in two layers of roofing material over the deck.


Structuralprecast, prestressed concrete members of characteristic cross-sectionused as roof and floor deck systems.

Double-lockstanding seam

Ina metal roof panel or metal cap, a standing seam that uses a doubleoverlapping interlock between two metal panels. Seestanding seam


Avertical pipe or conduit used to carry runoff water from a scupper,conductor head or gutter of a building to a lower roof levelor to the ground or storm water runoff system; also called aconductor or leader.


Theexternal force, for example, from the weight of ice and snow, appliedto a steep-slope roof system component forcing thecomponent downslope.


Anoutlet or other device used to collect and direct the flow of runoffwater from a roof area.


Aseparate layer of material that provides a location for moisture tomove laterally through a protected-membrane roof system.A drainage course relieves hydrostatic pressure from a material’ssurface and the associated weight of water.


Afabric composite or a nondegradable plastic configured to allowdrainage of water, typically with adhered filter fabric to preventgrowth medium and fines from blocking the drainage path.


Ametal flashing or other overhanging component with an outwardprojecting lower edge intended to control the direction ofdripping water and help protect underlying building components.


(1)Free or relatively free from a liquid, especially water; (2) toremove water or moisture.

Drybulb temperature

Thetemperature of air as measured by an ordinary thermometer.

Dryfilm thickness

Thethickness, expressed in mils, of an applied and cured coating ormastic. For comparison, see wet film thickness

Dry-in(or dry-in felt)

Usuallythe underlayment or the process of applying the underlayment forsteep-slope roofing. In low-slope roofing, it is usuallycalled a temporary roof.


Thetime required for the loss of volatile components so that thematerial will no longer be adversely affected by weather conditionssuch as dew, rain or freezing.


Theability to withstand physical, chemical or environmental abuse.


Anyload that is nonstatic, such as a wind load or moving live load.

Eave(Includes illustration)

The lower edge of a sloping roof; that part of a roof which projectsbeyond the wall.


Polyepichlorohydrin,commonly referred to as epichlorohydrin. See epichlorohydrin


Thepractice of providing regularly spaced or continuously protected(louvered or otherwise shielded) openings along a roofedge or perimeter, used as part of a ventilation system to dissipateheat and moisture vapor.


Anencrustation of soluble salts, commonly white, deposited on thesurface of stone, brick, plaster or mortar; usually causedby free alkalies leached from mortar or adjacent concrete as moisturemoves through it.


Seeexterior insulation and finish system


Seeethylene interpolymers


Theproperty of a body that causes it to tend to return to its originalshape after deformation (such as stretching, compres- sionor torsion).


Amacromolecular material that returns rapidly to its approximateinitial dimensions and shape after substantial deforma- tionby a weak stress and subsequent release of that stress.


Acoating that is capable of being stretched at least twice itsoriginal length (100 percent elongation) and recovering to its originaldimensions.


Amethod of application of corrosion-resistant zinc coatings forfasteners.


Theratio of the extension of a material to the length of the materialprior to stretching. Usually, elongation is expressed as apercentage of the original length.


(1)The process of pressing/positioning a felt, aggregate, fabric, mat orpanel into hot bitumen or adhesive to ensure contactat all points; (2) the process of pressing/positioning granules intocoating in the manufacture of factory-prepared roofing,such as shingles.


Theloss of flexibility or elasticity of a material.


(1)Infrared emissivity is a measure of the ability of a surface to shedsome of its absorbed heat (in the form of infrared radiation)away from the surface; emissivity is expressed as a percentage or adecimal factor; (2) the ratio of radiant ener- gyemitted from a surface under measurement to that emitted from a blackbody (the perfect emitter and absorber) at the sametemperature.


(1)A bituminous emulsion is a mixture of asphalt and water with uniformdispersion of the bitumen or water globules, usuallystabilized by an emulsifying agent (clay or soap) or system; (2) arelatively stable mixture of two immiscible liquids heldin suspension by small amounts of emulsifiers.


Thedistance of overlap where one ply, pane or piece extends beyond theend of the immediately adjacent underlying ply, panelor piece.


Thedistance of overlap where one ply, pane or piece extends beyond theend of the immediately adjacent underlying ply panelor piece.


Acontinuous membrane edge seal formed at the perimeter and atpenetrations by folding the base sheet or ply over the pliesabove and securing it to the top of the membrane. The envelopeprevents bitumen seepage from the edge of the membrane.


Ethylenepropylene diene M-class rubber, also called ethylene propylene dieneterpolymer. See ethylene propylene diene terpolymer


Asynthetic rubber including two epichlorohydrin-based elastomers. Itis similar to and compatible with EPDM.


Aclass of synthetic, thermosetting resins that produce tough, hard,chemical-resistant coatings and adhesives.


Seeexpanded polystyrene

Equiviscoustemperature (EVT)

Thetemperature at which a bitumen attains the proper viscosity forbuilt-up membrane application.

Equiviscoustemperature (EVT) application range

Therecommended bitumen application temperature range. The range isapproximately 25 F above or below the EVT, thus givinga range of approximately 50 F. The EVT range temperature is measuredin the mop cart or mechanical spreader just priorto application of the bitumen to the substrate.

Equiviscoustemperature (EVT) for asphalt

Therecommended EVT for roofing asphalt (ASTM D312, Type I, II, III orIV) is as follows:” mop application: the tempera- tureat which the asphalt’s apparent viscosity is 125.” “ mechanicalspreader application: The temperature at which the asphalt’sapparent viscosity is 75 centipoise.” “ Note: To avoid the use oftwo kettles if there are simultaneous mop and mechanicalspreader applications, the EVT for mechanical spreader applicationcan be used for both application tech- niques.”

Equiviscoustemperature (EVT) for coal tar

Therecommended EVT for roofing coal tar (ASTM D450, Type I or III) isthe temperature at which the coal tar’s apparent viscosityis 25 centipoise.


(1)Weathering, wearing away or degradation; (2) wearing away of acoating by chalking or the abrasive action of water or windborneparticles or grit.

Ethyleneinterpolymers (EIPs)

Agroup of thermoplastic compounds generally based on PVC polymers fromwhich certain single-ply roofing membranes canbe formulated.

Ethylenepropylene diene terpolymer (EPDM)

Aterpolymer of ethylene, propylene and diene with the residualunsaturated portion of the diene in the side chain to providefor vulcanization. It is a thermosetting synthetic elastomer. EPDM isan acronym for “ethylene propylene diene M-classrubber,” which is a name assigned to this material within theclassification established in ASTM D1418.


Seeequiviscous temperature

Expandedpolystyrene (EPS)

Atype of plastic foam insulation product having predominatelyclosed-cell structure manufactured from expanded poly- styrenebeads in a molding process; boards or blocks are formed. Seeinsulation


Theincrease in length or volume of a material or body caused bytemperature, moisture or other environmental condi- tions.


Astructural separation between two building elements that allows freemovement between the elements without damage tothe roof or waterproofing system.


(1)The transverse dimension of a roofing element or component notoverlapped by an adjacent element or component ina roof covering. For example, the exposure of any ply in a built-uproof membrane may be computed by dividing the feltwidth, minus 2 inches, by the number of shingled plies; thus, theexposure of 36-inch-wide felt in a shingled, four-ply membraneshould be approximately 8 1/2 inches; (2) the dimension of sidewallor roof covering that is not covered or overlappedby the up slope course of component. The typical exposure for astandard-size, three-tab shingle is 5 inches. Thisvaries depending on manufacturer specifications.

Exteriorinsulation and finish system (EIFS)

Anonload-bearing outdoor wall finish system consisting of a thermalinsulation board, attachment system, reinforcement systemand compatible finish.

Extrudedpolystyrene (XPS)

Atype of plastic foam insulation product manufactured by a continuousextrusion process as the resin foams. This forms atight and complete skin on each side of the board. See insulation


Aprocess in which heated or unheated material is forced through ashaping orifice (a die) in one continuously formed shape,as in film, sheet, rod or tubing.


(1)A woven cloth or material of organic or inorganic filaments, threadsor yarns used for reinforcement in certain mem- branesand flashings; (2) geotextile membranes used as a protective orseparating layer in roof and waterproofing sys- tems.


Theoutermost adhered top or bottom, or both, sheet (or layer) of aninsulation board that is composed of a different ma- terialthan the insulation itself. It is commonly composed of organic paper,glass mat or a combination thereof; generally impregnatedor coated, or both, with asphalt, latex, or other like material; ormetal foil.


Anylightening of initial color.


Areduction in bitumen softening point sometimes caused by refluxing oroverheating in a relatively closed container. See softeningpoint drift


(1)In steep-slope roofing, a board that is nailed to the ends of a roofrafter; sometimes supports a gutter; (2) in low-slope roofing,the vertical or steeply sloped roof or trim located at the perimeterof a building. Typically, it is a border for a low- sloperoof system.


Anyof a wide variety of mechanical securement devices and assemblies,including nails, staples, screws, cleats, clips and bolts,that may be used to secure various components of a roof assembly.


Aflexible sheet manufactured by the interlocking of fibers with abinder or through a combination of mechanical work, moistureand heat. Felts are manufactured principally from wood pulp andvegetable fibers (organic felts), asbestos fibers (asbestosfelts), glass fibers (fiberglass felts or ply sheets) or polyesterfibers.


Insulationcomposed principally of cellulose fibers usually derived from paper,paperboard stock or wood, with or without binders.See insulation

Fiberglassbase sheet

Afiberglass-reinforced base sheet for built-up roof systemconstruction, impregnated and coated with asphalt and sur- facedwith mineral matter; classified by ASTM D4601 as Type I or Type II.


Blanketor rigid board insulation composed of glass fibers bound togetherwith a binder, faced or unfaced, used to insulate roofsand walls.


Anasphalt roofing reinforcement manufactured from glass fibers.


Arelatively inert ingredient added to modify physical characteristics.See “stabilizer.”


Aheavy bead of waterproofing compound or sealant material generallyinstalled at the point where vertical and horizontal surfacesmeet to obtain a more gradual transition through the 90-degree angleat the base of a vertical flashing.


Sheetinghaving a nominal thickness not greater than 10 mils (0.010 inch).


Thethickness of a membrane or coating. Wet film thickness is thethickness of a coating as applied. Dry film thickness is thethickness after curing. Film thickness is usually expressed in mils(thousandths of an inch).


Atightly woven fabric, typically polyester orpolyethylene/polypropylene, used to restrict the flow of fineparticles and oth- ercontaminants while allowing water to pass freely through. It is usedto protect drainage systems from clogging.


Aterm used to describe a deck surface condition. A sharp raised edge(generally in concrete) capable of damaging a roof membraneor vapor retarder.

Finemineral surfacing

Water-insoluble,inorganic material, more than 50 percent of which passes through aNo. 35 sieve. Used on the surface of variousroofing materials and membranes to prevent sticking.


Gradebased on standard testing procedures of various materials.


Theproperty of materials or their assemblies that prevents or retardsthe passage of excessive heat, hot gases or flames underconditions of use.

Fire-retardant-treated(FRT) plywood

Plywoodthat has been impregnated under pressure with mineral salts; in theevent of fire, the burning wood and salts emit noncombustiblegases and water vapor instead of the usual flammable vapors.


Materialsused to limit the spread of fire.


(1)A half-cylindrical or half-conical shaped opening or void in a lappededge or seam, usually caused by wrinkling or shift- ingof ply sheets during installation (also referred to as an edgewrinkle); (2) in shingles, a half-conical opening formed at a cutedge.


Thepropagation of a flame away from its source of ignition.


Thosecharacteristics of a material that pertain to its relative ease ofignition and ability to sustain combustion.


Subjectto easy ignition and rapid flaming combustion.


Theprojecting edge of a rigid or semirigid component, such as an edgemetal flashing flange.


Thelowest temperature at which vapors above a combustible substanceignite in air when exposed to an ignition source.


Componentsused to weatherproof or seal roof system edges at perimeters,penetrations, walls, expansion joints, valleys, drainsand other places where the roof covering is interrupted orterminated. For example, membrane base flashing covers theedge of the field membrane, and cap flashings or counterflashingsshield the upper edges of the base flashing.


Atrowelable mixture of solvent-based bitumen and mineral stabilizersthat may include asbestos or other inorganic or or- ganicfibers. Generally, flashing cement is characterized asvertical-grade, which indicates it is intended for use on vertical surfaces.See asphalt roof cement and plastic cement


Amethod of interlocking metal panels in which one panel edge is foldedback on top of itself and the other panel is folded under,after which the two panels are hooked together.


Matsor felts composed of fibers, sometimes used as a membrane backer.

Flood(pour) coat

Thesurfacing layer of bitumen into which surfacing aggregate is embeddedon an aggregate-surfaced built-up roof.


Amembrane-integrity test conducted by temporarily plugging orotherwise closing any drains and erecting temporary damswhere required to retain water on the surface of a waterproofingmembrane and then flooding the surface to a maxi- mumdepth of 2 inches at the high point and retaining the water for aminimum of 24 hours or as required by the manufac- turer.See water testing


Theability of a coating to move freely as a liquid, allowing it toachieve a level surface.


Amembrane integrity test conducted by applying continuously flowingwater over a waterproofing membrane’s surface withoutclosing drains or erecting dams for a minimum of 24 hours or asrequired by the manufacturer. See water testing


Fluorine-substitutedethylene polymers, featuring outstanding formability, heatresistance, color retention, and resistance tosolvents and chalking.


Inmetal decking, the space corresponding to the rib depth bound by theweb sections.


Abituminous material used as feed stock for further processing and asa material to soften other bituminous materials.


Commonlyreferred to as FM, a research and testing business unit of FM Global(a commercial and industrial property insurer)that classifies roofing components and assemblies for their fire,traffic, impact (hail), weathering and wind-uplift resistance.


Theroof edge treatment upon which spray polyurethane foam (SPF) isterminated.


Astrength or energy exerted or brought to bear; cause of motion orchange.


ForestProducts Laboratory.


Thefreezing and subsequent thawing of material.


Resistanceto cycles of freezing and thawing that could affect applications,appearance or performance.


Thetendency of material or product to crumble or break into small pieceseasily.

G-60and G-90

Designationsfor galvanized metal sheet, indicating 0.60 ounces and 0.90 ounces ofzinc per square foot, respectively; a combinedmeasure of zinc coating on both sides.

Gable(Includes illustration)

The vertical triangular portion of the end of a building hav- inga double-sloping roof from the level of the eaves to the ridge of theroof.


ABIEC International Inc.-trademarked name for a metal alloy coatingthat is composed of 55 percent aluminum, 43.4 percentzinc and 1.6 percent silicon. It is also known by various other tradenames such as Zincalume,™ Zintro-Alum™ and Galval.™


Anelectrochemical action that generates electrical current between twometals of dissimilar electrode potential.


Alist of metals and alloys arranged according to their relativeelectrolytic potentials in a given environment.


Steelcoated with zinc for corrosion resistance.


(1)A roof that has two pitches on each side of a central ridge where theupper roof areas have less slope than the lower roofareas; (2) a roof with two inclines on each slope.


Ametal thickness measurement; a smaller gauge number indicates athicker metal.


Aprefabricated water drainage material used to relieve hydrostaticpressure against waterproofing and promote drainage.


Atightly woven fabric used to restrict the flow of fine soil particlesand other contaminants while allowing water to freely passthrough; used to protect drainage systems from clogging.


Ahorizontal beam that supports wall cladding between columns.


Glassfibers bonded into a sheet with resin and suitable for impregnationwith asphalt in the manufacture of bituminous waterproofing,roof membranes and shingles.

Glassfiber insulation

Seefiberglass insulation


Athin mat of glass fibers with or without a binder.


(1)The top layer of asphalt on a smooth-surfaced built-up roof membrane;(2) a thin protective coating of bitumen applied tothe lower plies or top ply of a built-up roof membrane whenapplication of additional felts or the flood coat and aggre- gatesurfacing are delayed.


Theshine, sheen or luster of a dried film or another surface.


(1)The term used when referring to the ground elevation around abuilding; (2) the classification of materials by quality or specifictype.


(1)The change in a variable quantity, as temperature or pressure perunit distance; may be represented by a curve of such arate of change; (2) the rate of change of a variable with respect toa measured quantity.

Graduatedslate roof

Aslate roof system in which successive slate courses diminish inlength and/or thickness from eave to peak.


Aunit of measure in the English System of units equal to 1/7,000 lb.;used in measuring atmospheric water vapor content.


Opaque,natural or synthetically colored aggregate commonly used to surfacecap sheets, shingles and other granule-sur- facedroof coverings; also referred to as mineral or ceramic granules.


Coarsegranular aggregate resulting from the natural erosion of rock.


Aflanged device, frequently metallic, designed to prevent looseaggregate from washing off the roof and to provide a con- tinuousfinished edge for the roofing.


Ata particular site, the level below which the subsoil and rock massesof the earth are fully saturated with water.


Amixture of cement, sand and water used to fill cracks and cavities inmasonry.


(1)Used at the bottom of a steep-slope roof system valley, a large flatmetal piece(s) wider than the valley to help prevent buildupat the base of the valley either from debris or ice-dam formations.(2) A plate used to connect two or more mem- bersor to reinforce a joint.


Achanneled component installed along the downslope perimeter of a roofto convey runoff water from the roof to the drainleaders or downspouts.

Gypsumboard panels

Cementitiousboard stock with noncombustible core primarily comprised of gypsumthat is commonly used as a barrier board,thermal barrier or cover board in a roof assembly.


Amixture of calcined gypsum binder and wood chips or other aggregate;when mixed with water, sets to a conglomerate mass;used for poured gypsum roof decks.


Amethod of spot-applying asphalt-based adhesive to shingles forsecurement and wind resistance. Also termed “hand-sealing.”


Commonname for asphaltic protection board used in waterproofingapplications. Hardboard products may consist of a combinationof asphalt-saturated organic (cellulosic) felt and coated orsaturated nonwoven glass felt or may be entirely glass-felt-based;classified by ASTM D6506.


(1)The distance of overlap measured from the uppermost ply or course tothe point where it laps over the undermost ply orcourse; (2) the head lap area.


Ahorizontal framing structural member of a door, window or otherframed opening.




Theheat flow rate through a surface of unit area perpendicular to thedirection of heat flow.


Thetransmission of thermal energy from a location of higher temperatureto a location of lower temperature. This can occurby conduction, convection or radiation.


Amethod of melting and fusing together the overlapping edges ofseparate sheets or sections of polymer-modified bitu- men,thermoplastics or some uncured thermoset roofing membranes by theapplication of heat (in the form of hot air or openflame) and pressure.


Tobe installed by heating the underside of the sheet with a propanetorch or other heating device, melting the polymer-modifiedbitumen on the bottomside and adhering the sheet in the moltenmaterial.


Theedge created by folding metal back on itself.

Hip(Includes illustration)

The sloping line along the outer angle formed by the meetingof two sloping sides of a roof with eaves that meet at a right angle.

Hiproof (Includes illustration)

A roof that rises by inclined planes from all four sides of a buildingto form hips at the intersection of adjacent roof slopes.


Acover, usually of light-gauge metal, over piping or other rooftopequipment.


Thecondition of the atmosphere with respect to water vapor. See relativehumidity


Heating,ventilating and air-conditioning equipment.


Thechemical reaction by which a substance (such as Portland cement)combines with water, giving off heat to form a crystallinestructure in its setting and hardening.


Anorganic chemical compound primarily containing the elements carbonand hydrogen. Hydrocarbons are divided into twogeneral classes—aliphatic and aromatic—differentiated by the typeof carbon-carbon bonds they contain. Aliphatic hydrocarbonsare straight chain compounds. Aromatic hydrocarbons contain one ormore benzene ring or naphthalene ringstructure.


Thepressure equivalent to that exerted on a surface by a column of waterof a given height.


Attracting,absorbing and retaining atmospheric moisture.


Aregistered trademark of E.I. du Pont de Nemours & Co. forchlorosulfonated polyethylene (CSPE). See chlorosulfonated polyethylene


InternationalBuilding Code. A model building code published by the InternationalCode Council (ICC); applies to all con- structionexcept detached one- and two-family dwellings and townhouses.


InternationalCode Council. A nonprofit organization dedicated to developing andmaintaining a single set of comprehen- sive,coordinated national building codes (I-Codes®); established in 1994by three major U.S. model building code bodies: BuildingOfficials and Code Administrators International Inc. (BOCA),International Conference of Building Officials (ICBO) andSouthern Building Code Congress International Inc. (SBCCI).

Icedam (Includes illustration)

A mass of ice formed at the transition from a warm to a coldroof surface, frequently formed by refreezing meltwater at theoverhang of a steep roof causing ice and water to back upunder roofing materials.


Resistanceto fracture under the sudden application of an exerted force.


Inroofing materials manufacture, to completely surround the fibers in afelt or mat with bitumen with the spaces between thefibers partially or completely filled without a continuous coating ofbitumen on the surface.


Thermalresistance value established under installed conditions and measuredduring the expected service life of the material.


Theslope of a roof expressed in percent or in units of vertical rise perunits of horizontal run.


Beingor composed of materials other than hydrocarbons and theirderivatives, or matter that is not of plant or animal origin.


Anyof a variety of materials designed to reduce the flow of heat from orinto a building. See thermal insulation


Afelt, metal or membrane sheet material used between courses ofsteep-slope roofing to improve the weather- and water-sheddingcharacteristics of the primary roof covering during times ofwind-driven precipitation; typically used with woodshakes.


Individualshingles that mechanically attach to one another to provide enhancedwind resistance without reliance on seal- ingstrips.


InternationalResidential Code; a model building code published by theInternational Code Council (ICC); applies to de- tachedone- and two-family dwellings and townhouses.


InternationalStaple, Nail & Tool Association.


Ahighly reactive organic chemical containing one or more isocyanategroups. A basic component in spray polyurethane foam(SPF) systems and some polyurethane coating systems. See A-component(A-side) and methylene diphenyl diiso- cynate(MDI)


Seeslip sheet


Anyof the small timbers, metal or wood beams arranged parallel to oneanother and spanning from wall to wall to support afloor, ceiling or roof of a building.


Aunit of energy or work in the SI system; equals the work done by aforce of 1 newton, which acts over a distance of 1 meterin the direction of the force.

Kor k-value

Thermalconductivity; the time rate of heat flow through a unit area of ahomogeneous material in a direction perpendic- ularto isothermal planes induced by a unit temperature gradient. InEnglish (inch•pound) units of measurement, it is the numberof Btu that pass through a 1-inch thickness of a 1-square-foot sampleof material in one hour with a temperature differencebetween the two surfaces of 1 degree Fahrenheit. It is expressed asBtu•in/hr•ft2•F.


Alower downspout section used to direct water away from a wall.

Kick-outflashing (diverter)

Ametal flashing detail installed at the eave end of a roof-to-walltransition designed to direct runoff away from the wall or wallcladding.


Aweak layer of cement and aggregate fines on a concrete surface thatis usually caused by an overwet mixture, overwork- ingthe mixture, improper or excessive finishing, or combination thereof.


Tojoin layers of materials together using fusion; the process ofjoining layers of materials together using adhesion.


See“dimensional shingles.”


Thatpart of a roofing, waterproofing or flashing component that overlapsor covers any portion of the same or another typeof adjacent component.


Anasphalt-based roof cement formulated to adhere overlapping plies orasphalt roll roofing.


Occurswhere overlapping materials are seamed, sealed or otherwise bonded.


(1)The action of removing soluble constituents from a solid into asolution; (2) the dissolving out of soluble substances whenwater seeps through a roof system.


Asoft, malleable, naturally weathering heavy metal; has low meltingpoint and a high coefficient of thermal expansion.


Thedirection opposite that from which the wind is blowing. The sidesheltered from the wind. For comparison, see “wind- ward.”

Life-cycleassessment (LCA)

Amethod of evaluating a product or system by reviewing the ecologicaleffect over its entire life. Life stages include ex- tractionof raw materials, processing and fabrication, transportation,installation, use and maintenance, and reuse, recy- clingand disposal. At each stage, the product or system and its componentsare evaluated based on materials and energy consumedand the pollution and waste produced. LCA is an environmental reviewmethodology.

Life-cyclecost analysis

Atechnique of economic evaluation that sums up the costs of a productor system during its entire life including raw materialsextraction, processing and fabrication, transportation, installation,use and maintenance, and reuse, recycling ordisposal. At each stage the product or system and its components areevaluated based on the costs of materials and energyconsumed and pollution and waste produced.


Thespray polyurethane foam (SPF) that results from a pass. It usually isassociated with a certain pass thickness and has abottom layer, center mass and top skin in its makeup.


Seeaggregate, lightweight


(1)Concrete with a density of less than 115 lb/ft”3″; (2) Poureddeck fill composed of a combination of two or more of the following:gypsum, vermiculite, perlite, wood fibers and air-entrained concrete.

Lightweightor insulating concrete fill (LWIC)

Concretemade with or without aggregate additions to Portland cement, waterand air to form a hardened material that whenoven dried will have a unit weight of 50 lb/ft”3″ or less.


Applicationof bituminous cements, adhesives or coatings installed at ambient orslightly elevated temperatures.

Liquid-appliedbuilt-up roof

Acontinuous, semi-flexible roof membrane consisting of multiple pliesof felts, mats or fabrics laminated together with alternatelayers of roof cements and surfaced with a liquid-applied coatingwith or without aggregate surfacing.


Temporaryloads that the roof structure must be designed to support, asrequired by governing building codes. Live loads aregenerally moving and/or dynamic or environmental (e.g., people,installation equipment, snow, ice, rain).


Inroofing: (1) production lot—all material produced in one eight-hourshift of the same type (and color when applicable); (2)delivery lot—all material of the same type delivered at one time byone truck or railroad car.


Acategory of roofs that generally includes weatherproof membrane typesof roof systems installed on slopes at or less than3:12.


Theability of a membrane or other material to resist cracking whenflexed after it has been cooled to a low temperature.

Mansard(Includes illustration)

A decorative steep-sloped roof on the perimeter of a building.


Plywoodthat is made entirely of Douglas fir or western larch with all veneerplies being Grade B or better and is sanded onboth faces or includes medium- or high-density overlay with maximumcore-gap sizes of 1/8 inch; is exterior-rated with fullywaterproof structural adhesive glue; and is not treated withdecay-resistance chemicals. Where decay is a concern, it shouldbe preservative-treated.


Construction,usually set in mortar, of natural building stone or manufacturedunits, such as brick, concrete block, adobe, glassblock, tile, manufactured stone or gypsum block.


Athick adhesive material used as a cementing agent for holdingwaterproofing membrane in place.


Athin layer of woven, nonwoven or knitted fiber that serves asreinforcement to a material or membrane.


Inroofing, physical damage to a roof system not caused by normal wearand tear.

Mechanicallyfastened membrane

Generallyused to describe a membrane that has been attached to the substrateat defined intervals.


Aflexible or semiflexible roof covering or waterproofing whose primaryfunction is to exclude water.


Tendencyof a material to regain its previous configuration.


Anyof various opaque, fusible, ductile and typically lustrous substancesthat are good conductors of electricity and heat.


Seeflashing; frequently used as through-wall-, step-, cap- orcounterflashing.

Metalrain collar

Ametal counterflashing used to wrap a penetration and prevent waterinfiltration through the top of the penetration base flashing.

Metalroof panel

Asheet-metal product having an installed weather exposure less than 3square feet per sheet.

Metalroof panel

Asheet-metal product having a minimum installed weather exposure of 3square feet per sheet.


Unitof length measurement in the SI system; 1 meter is equal to 39.37inches.

Methylenediphenyl diisocynate (MDI)

TheA-component (A-side) in spray polyurethane foam (SPF). An organicchemical compound having two reactive isocya- nategroups. It is mixed with the B-component to form polyurethane in achemical reaction.


Aunit of measure, one mil is equal to 0.001 inches; often used toindicate the thickness of a roof membrane.


Asuperficial growth produced on organic matter or living plants byfungi.


Insulationcomposed principally of fibers manufactured from rock, slag or glass,with or without binders.




Roofingmaterials with a surface or top layer consisting of agranule-surfaced sheet.


Seepolymer-modified bitumen


Asurface growth of fungus on damp or decaying matter. The term has notaxonomic significance and is used only in a generalsense of visible fungal growth on organic matter. See mildew


Alow-molecular-weight substance consisting of molecules capable ofreacting with like or unlike molecules to form a polymer.

Mopand flop

Anapplication procedure in which roofing elements (insulation boards,felt plies, cap sheets, etc.) are initially placed upsidedown adjacent to their ultimate locations; coated with adhesive orbitumen; and turned over and adhered to the substrate.


Theapplication of hot bitumen with a mop or mechanical applicator to thesubstrate or plies of a bituminous membrane. Thereare two types of mopping as follows:” mopping, solid: A continuouscoating,” “ “””mopping, spot: Bitumen is applied roughlyin circular areas, leaving a grid of unmopped perpendicular areas.”


Seematerial safety data sheet


NationalAssociation of Home Builders.


(Sometimesreferred to as “blocking”); a piece or pieces of dimensionallumber and/or plywood secured to a structural deckor walls that provides a receiving medium for the fasteners used toattach membrane or flashing. See blocking (1)


Amember, usually of wood, set into or secured to nonnailable roofdecks or walls to allow for positive anchorage by nail- ingof roofing felts, insulation or flashings.


Acrylonitrilebutadiene polymer blend. One proprietary NBP membrane is commonlyreferred to as nitrile-butadiene copo- lymer.


Anapplication wherein the waterproofing system and source ofhydrostatic pressure are on opposite sides of the structur- alelement.


Asynthetic rubber (polychloroprene) used in liquid- or sheet-appliedelastomeric roof membranes or flashings.


(1)The installation of new metal roof deck directly on top of existingmetal roof deck; (2) a method of reroofing with new asphaltshingles over existing shingles in which the top edge of the newshingle is butted against the bottom edge of the existingshingle; also known as “butt-and-run method.”


SIunit of measure for force.


NationalFire Protection Association; an international nonprofit organization.Its mission is to reduce the worldwide burden offire and other hazards on the quality of life by providing andadvocating consensus codes and standards, research, trainingand education. NFPA publishes the NFPA 70, “National ElectricalCode” (NEC).


NationalInstitute of Standards and Technology.


Anelastomeric material of synthetic nonvulcanizing polymers.


NationalOceanic and Atmospheric Administration.


Ametal that readily receives electrons from an anodic metal (seegalvanic series) but does not readily give up its own electrons;characterized by a marked resistance to chemical reaction,particularly to oxidation and to solution by inorganic acids.

Nondestructivetesting (NDT)

Amethod to evaluate the disposition, strength or composition ofmaterials or systems without damaging the object under test.Typically used to evaluate moisture content in roofing assemblies,the three common test methods are electrical capacitance,infrared thermography and nuclear back-scatter.


Metalthat is not an iron alloy and is nonmagnetic (e.g., aluminum,copper).


Atextile structure produced by bonding or interlocking of fibers, orboth, accomplished by mechanical, chemical, thermal, orsolvent means and combinations thereof.


NationalRoofing Contractors Association.


Genericname for a family of polyamide polymers used as a scrim in somefabric-reinforced sheeting.


Spraypolyurethane foam (SPF) that has excess isocyanate or resin.Off-ratio SPF will not exhibit the full physical proper- tiesof correctly prepared SPF.


Anunsaturated open-chain hydrocarbon containing at least one doublebond: ethylene or propylene.


Theperiod of time after an adhesive has been applied and allowed to dryduring which an effective bond can be achieved byjoining the two surfaces.

Openvalley (Includes illustration)

A method of valley construction in which the steep- sloperoof-covering materials on both sides are trimmed along each side ofthe valley, exposing the metal valley flashing.

Orange-peelsurface texture

Inspray polyurethane foam (SPF) roofing, a condition of the foam inwhich the surface shows a fine texture and is com- paredto the exterior skin of an orange. This surface is consideredacceptable for receiving a protective coating.


Beingor composed of hydrocarbons or their derivatives; matter of plant oranimal origin.


Anasphalt roofing base material manufactured from cellulose fibers. See“felt.”

Orientedstrand board (OSB)

Amat-formed panel product with oriented layers resulting indirectional properties. OSB is comprised primarily of wood strandsbonded with exterior adhesive formulations under heat and pressure.Design capacities are referenced to the pri- maryand secondary structural axes, which typically correspond to themanufacturing machine and cross-machine direc- tions,respectively. The primary direction is often referred to as thestrength direction.


OakRidge National Laboratory.


OccupationalSafety and Health Administration; a government agency in the U.S.Department of Labor. Its mission is to maintaina safe and healthy work environment.


Anymaterial installed on top of a waterproofing assembly.


Component(s)in a roof or waterproofing drainage system used to protect it againstdamage from a water load imposed byblocked or partially blocked primary drainage system; e.g., overflowscupper, overflow interior drain.


See“roof overhang.”


Undesirabledepositions of airborne spray.


(1)A weathering mechanism of materials exposed to the elements; can bepromoted by elevated temperature, ultraviolet radiation,galvanic action and other agents; (2) loss of electrons by aconstituent of a chemical reaction; sometimes, more specificallythe combination of oxygen with a reactant.


Atriatomic form of oxygen that is a bluish gas of pungent odor,chemically very active; formed naturally in the upper atmo- sphereby a photochemical reaction with solar ultraviolet radiation.


Aplatform (typically wooden) used for storing and shipping materials.


Thebottom flat part of a roofing panel that is between the ribs of thepanel.


Thepart of a perimeter wall that extends above a roof.


Amaterial applied to one or both surfaces of a sheet to preventsticking. Examples include fine mineral aggregate such as sandor crushed blast furnace or boiler slag and applications of siliconeoils or surfactants; also called “release agent.”


SIunit of measure for force per unit area (load, shear stress); 1 Pa=1N/m”2″=0.2089 lb/ft”2″.


(1)A layer of material, usually applied by the spray method, that isallowed to reach cure before another layer (“pass”) is applied;(2) a term used to explain a spray motion of the foam gun in theapplication of the spray polyurethane foam (SPF) material.The speed of the pass controls the thickness of the SPF.


Typicallyused in reference to aluminum-based coatings; for aluminum coatings,the amount of aluminum flake typically is lessthan the amount of paste.


Asupport or base for rooftop components such as pavers, pipes andsmall rooftop units.


Theaverage load per unit width required to separate progressively aflexible member from a rigid member or another flexiblemember.


(1)Any construction (e.g., pipes, conduits, HVAC supports) passingthrough a roof; (2) the consistency of a bituminous materialexpressed as the distance, in tenths of a millimeter (0.1 mm), that astandard needle penetrates vertically into asample of material under specified conditions of loading, time andtemperature (ASTM D5 is the test method used for bituminousmaterials). A cone is sometimes used for special purposes instead ofa needle.


Bitumen-saturatedfelt perforated with closely spaced small holes to allow air andmoisture to escape during application ofbuilt-up roofing; depending on the type of material or specific use,can be classified in accordance with ASTM D226, D2626or D4897 requirements.


Anaggregate used in lightweight insulating concrete and preformedperlitic insulation boards, formed by heating and expandingsiliceous volcanic glass.




(1)The time rate of vapor transmission through unit area of flatmaterial of unit thickness (values in reference sources are quotedfor unit thicknesses) induced by unit vapor pressure differencebetween two specific surfaces under specified tem- peratureand humidity conditions. The English (inch•pound) unit ofmeasurement for permeability is (grains•in.)/(h•ft2•in. Hg),which is commonly referred to as “perm•inch” units; (2) Theproperty of a porous material that permits a fluid (or gas) topass through it; commonly refers to water vapor permeability of asheet material or assembly and is defined as water vaporpermeance per unit thickness.


(1)The time rate of water vapor transmission through unit area of flatmaterial or construction induced by unit vapor pres- suredifference between two specific surfaces (values in reference sourcesare quoted for specific material thicknesses) underspecified temperature and humidity conditions. The English(inch•pound) unit of measurement for permeance is (grains)/(h•ft2•in.Hg), which is commonly referred to as “perm” units.


(1)The installation of a roof or waterproofing system during two or moreseparate time intervals or different days. Appli- cationsof surfacings at different time intervals are typically notconsidered phased application. See surfacing (2) A roof systemnot installed in a continuous operation.


Aclosed-cell, rigid, thermosetting foam insulation product with anorange or light-red foam core. Facer materials include corrugatedcellulose, aluminum foil and fiberglass mat. See insulation Phenolicfoam roof insulation can contribute to corrosionof steel roof decks because of leaching out of acidic compounds thattakes place when the phenolic foam roof insulationcontacts moisture.


Aninsoluble compounding material used to impart color.


PolyisocyanurateInsulation Manufacturers Association.


Atiny hole in a coating, film, foil, membrane or laminate comparablein size to one made by a pin.


Seecoal tar or roof slope


Aflanged, open-bottomed enclosure made of sheet metal or othermaterial placed around a penetration through the roof, properlystripped-in to the roof membrane and filled with grout and bituminousor polymeric sealants to seal the area aroundthe penetration.


Awood deck of planks usually 1 5/8 inches to 3 1/2 inches thick and 6inches to 8 inches wide laid on the flat tongued- and-groovedor splinted edges and spiked together.


Aroofing industry generic term used to describe asphalt roof cementthat is a trowelable mixture of solvent-based bitu- men,mineral stabilizers, and other fibers and/or fillers; generally it isintended for use on relatively low slopes, not vertical surfaces.See “asphalt roof cement” and “flashing cement.”


Liquidor solid additives used to impart flexibility to a hard, rigidpolymer such as PVC or nitrocellulose.


Insome thermoplastic roof membranes, the loss of plasticizer chemicalsfrom the membrane resulting in shrinkage and embrittlementof the membrane.


Thematerial property of being flexible or moldable.


Alayer of felt or ply sheet in a built-up roof membrane or roofsystem.


Aflat panel built up of sheets of wood called veneers, united underpressure by a bonding agent to create a panel with an adhesivebond between plies as strong as or stronger than the wood. Plywood isconstructed of an odd number of layers withgrain of adjacent layers perpendicular. Layers may consist of asingle ply or two or more plies laminated with parallel graindirection. Outer layers and all odd-numbered layers generally havethe grain direction oriented parallel to the long dimensionof the panel.


Seeprotected membrane roof (PMR)


Apolymer in which the repeated structural unit in the chain is of theester type.


Aproduct formed by the polymerization of isobutylene; may becompounded for use as a roof membrane material.


Acellular, unfaced, preformed rigid thermal insulation produced by thepolymerization of polyisocyanates in the presence ofpolyhydroxyl compounds, catalysts, cell stabilizers, and blowingagents; classified in accordance with ASTM C591.

Polyisocyanuratefoam board

Athermal insulation composed of polyisocyanurate foam with adheredfacers; commonly called iso or isoboard; classified inaccordance with ASTM C1289.


Amacromolecular material formed by the chemical combination ofmonomers having the same or different chemical composition.


(1)A bitumen modified by including one or more polymers (e.g., atacticpolypropylene, styrene butadiene styrene); (2) compositesheets consisting of a polymer-modified bitumen often reinforced withvarious types of mats or films and sometimessurfaced with films, foils or mineral granules.

Polymericmethylene diphenyl diisocyanate (PMDI)

Seemethylene diphenyl diisocynate (MDI)


Achemical reaction in which monomers are linked together to formpolymers.


Apolyhydric alcohol (one containing three or more hydroxyl groups);the main ingredient of the resin component (B-com- ponentor B-side) of polyisocyanurate and polyurethane compounds. See resin(1)


Apolymer prepared by the polymerization of propylene as the solemonomer.


Apolymer prepared by the polymerization of styrene as the solemonomer.


Apolymer prepared by the reaction of an organic diisocyanate withcompounds containing hydroxyl groups (polyols). Polyurethanes,or urethanes as they are sometimes called, may be thermosetting,thermoplastic, rigid or soft and flexible, cellularor solid; they can be aliphatic or aromatic. See aliphaticpolyurethane and aromatic polyurethane


Aone- or two-part solvent-based coating that contains polyisocyanatemonomer and a hydroxyl containing resin, that reactsduring cure to form elastomeric coating.

Polyurethanefoam (cellular polyurethane)

Insulationcomposed principally of the catalyzed reaction product ofpolyisocyanate and polyhydroxy compounds, pro- cessedusually with fluorocarbon gas to form a rigid foam having apredominately closed-cell structure. It is sprayed-in- placeor preformed into boards. See insulation

Polyvinylchloride (PVC)

Asynthetic thermoplastic polymer prepared from vinyl chloride. PVC canbe compounded into flexible and rigid forms throughthe use of plasticizers, stabilizers, fillers and other modifiers.Rigid forms are used in pipes; flexible forms are usedin the manufacture of sheeting and roof membrane materials.

Polyvinylidenefluoride (PVDF)

Ahighly nonreactive thermoplastic fluoropolymer. PVDF known by theregistered trade names of Kynar 500® and Hylar 5000®is used as the principal ingredient in high-quality paints andprotective coatings for metals, including architectural sheetmetal and metal roofing applications. PVDF coatings have good glossand color retention and are reported to resist chalking,cracking and fading.


Theexcessive accumulation of water at low-lying areas on a roof thatremains after 48 hours after precipitation under conditionsconducive to drying.

Popcornsurface texture

Inspray polyurethane foam (SPF) roofing, the condition in which thefoam surface shows a coarse texture where valleys formsharp angles. This surface is unacceptable for proper coating andprotection.


Ahydraulic (sets and hardens by chemical reaction with water and iscapable of doing so under water) cement used for makingconcrete and grout. Portland cement is a mixture that consists ofcalcium carbonate and clay-like minerals or othersilica-, alumina- and iron-oxide bearing materials; various types areformulated and manufactured.


Thedrainage condition in which consideration has been made during designfor all loading deflections of the deck and additionalroof slope has been provided to ensure drainage of the roof areawithin 48 hours of precipitation.

Potlife (working life)

Theperiod of time during which a reacting composition remains suitablefor its intended processing after mixing with reactioninitiating agents.


Seeflood (pour) coat


Atype of sealant often supplied in two parts and used atdifficult-to-flash penetrations, typically in conjunction with pene- trationpockets to form a seal.


Coatinga metal with solder or tin alloy prior to soldering or brazing it.


Aterm used to describe a category of adhesives that in dry(solvent-free) form are tacky at room temperature and adhere toa variety of dissimilar surfaces when contact is promoted byapplication of pressure. Pressure-sensitive adhesives do notrequire activation by an energy source such as heat.


Concretein which the reinforcing cables, wires or rods are tensioned beforethere is load on the structural member, hold- ingthe concrete in compression for greater strength.


Drainagedevices, such as drains or scuppers, that provide for the directremoval of water from a waterproofing system.


(1)A thin, liquid-applied solvent-based bitumen that may be applied to asurface to improve the adhesion of subsequent applicationsof bitumen; (2) a material that is sometimes used in the process ofseaming single-ply membranes to prepare thesurfaces and increase the strength (in shear and peel) of the fieldsplice; (3) a thin liquid-applied material that may beapplied to the surface of spray polyurethane foam (SPF) to improvethe adhesion of subsequent application of SPF protectivecoatings.

Protectedmembrane roof (PMR)

Aninsulated and ballasted roof assembly in which the insulation andballast are applied on top of the membrane (some- timesreferred to as an inverted roof assembly).


(1)A sacrificial material used to shield a waterproofing material fromdamaging external forces; (2) a separate layer of materialinstalled on top of the membrane to protect a vegetative roofwaterproofing membrane from damage.


Asacrificial material used to shield one roof system component fromanother.


Poundsper square inch.


Achart showing the relationship between dew point temperature, drybulb temperature, wet bulb temperature and relative humidity.


Theability of a material to withstand the action of a penetrating orpuncturing object.


Ahorizontal secondary structural member that transfers loads to theprimary structural framing.


Seepolyvinyl chloride (PVC)


Seepolyvinylidene fluoride (PVDF)


Seethermal resistance (R)


Amethod of asphalt shingle application also referred to as the“straight-up method,’ whereby shingle courses are applied verticallyup the roof rather than laterally or across and up; requires placinga part of a shingle under product already in placeevery other course, which may result in a less-than-recommendednumber of nails being used for fastening.


Oneof a series of sloped structural members that extend from the ridgeor hip to the downslope perimeter or eave de- signedto support the roof deck or secondary horizontal structural memberssuch as purlins and the associated loads.


Agroove or slot often cut in a masonry wall or other vertical surfaceadjoining a roof for inserting an inset flashing compo- nentsuch as a reglet.

Rake(Includes illustration)

The sloped edge of a roof at or adjacent to the first or last rafter.


RoofConsultants Institute. The former name of RCI Inc.—The Institute ofRoofing, Waterproofing & Building Envelope Pro- fessionals,an international nonprofit association of roofing, waterproofing, andbuilding envelope specification and design consultants.


RoofCoatings Manufacturers Association.


Theprocess of installing an additional roof covering over a preparedexisting roof covering without removing the existing roofcovering.


Acomponent in a two-piece counterflashing that may be surface-mountedto a wall, inset into a raggle or embedded be- hindcladding. It is used for ease of installation and future maintenanceand repair or replacement. See reglet


Solarreflectance is the fraction of the solar energy (flux) that isreflected by the surface; reflectivity is expressed as a per- centageor a decimal value between 0.00 and 1.00.


Definedas the reflectance of an opaque, optically flat surface or coating ofthickness sufficient to be a completely opaque.Reflectivity is a property of a material, while “reflectance” isa property of a sample of the material.


Asheet-metal receiver for the attachment of counterflashing. A regletmay be surface-mounted, inset into a raggle or embeddedbehind cladding.


Aroof or waterproofing membrane that has been strengthened by theaddition or incorporation of one or more reinforcing materials,including woven or nonwoven glass fibers, polyester mats or scrims,nylon or polyethylene sheeting.

Relativehumidity (RH)

Theratio of the pressure of water vapor present in a given volume of airto the pressure of fully saturated water vapor at thesame temperature, expressed as a percentage.


Theprocess of removing the existing roof covering, repairing any damagedsubstrate and installing a new roof covering; alsoknow as “tear-off and replacement.”


Theprocess of recovering or replacing an existing roof covering. Seere-cover and replacement


(1)In spray polyurethane foam (SPF) roofing, the B-component (B-side).This component contains a catalyst, blowing agent,fire retardants, surfactants and polyol. It is mixed with theA-component (A-side) to form polyurethane; (2) in plas- ticsmanufacturing, any polymer that is a basic material for plastics; (3)in grouting, a material that usually constitutes the baseof an organic grout system.


Themodification of an existing building or facility to include newsystems or components.

Ridge(Includes illustration)

Highest point on a roof, represented by a horizontal line wheretwo roof areas intersect, running the length of the area.


Ahorizontal board in wood frame construction at the upper end of thecommon rafters to which the rafters are nailed.


Amaterial or covering applied over the ridge of a roof.


Thelast or top course of roofing materials, such as tile, roll roofing,shingles, that covers the ridge and overlaps the inter- sectingfield roofing.


Aventilator located at the ridge that allows the escape of warm and/ormoist air from the attic area or rafter cavity.




Ageneral term applied to rolls of roofing felt, ply sheet, etc., thatare typically furnished in rolls.


Coatedfelts, either smooth or mineral-surfaced.


(1)The cover of a building; (2) to cover with a roof.

Roofarea divider

Seearea divider


Anassembly of interacting roof components including the roof deck,vapor retarder (if present), insulation and membrane orprimary roof covering designed to weatherproof.


Seeasphalt roof cement and coal-tar roof cement


Theexterior roof cover or skin of the roof assembly consisting ofmembrane, panels, sheets, shingles, tiles, etc.


Raisedframe used to mount mechanical units such as air conditioning units,exhaust fans, skylights, etc., on a roof.


Theangle a roof surface makes with the horizontal, expressed as a ratioof the units of vertical rise to the units of horizon- tallength (sometimes referred to as run). For English units ofmeasurement, when dimensions are given in inches, slope maybe expressed as a ratio of rise to run, such as 4:12, or as an anglein degrees.


Amethod of asphalt shingle application also referred to as the“straight-up method” whereby shingle courses are applied verticallyup the roof rather than laterally or across and up; requires placinga part of a shingle under product already in placeevery other course, which may result in a less-than-recommendednumber of nails being used for fastening.

Rosinpaper (specifically rosin-sized sheathing paper)

Anonasphaltic paper used as a sheathing paper or slip sheet in someroof systems.


Amaterial that is capable of recovering from large deformationsquickly and forcibly.


Horizontaldimension of a slope.


(1)A reddish material, primarily hydrated iron oxide; a corrosionproduct formed on iron or its alloys, resulting from ex- posureto a humid atmosphere or chemical attack; (2) a special case ofcorrosion that deteriorates or alters the original surfacecondition.


Theform of corrosion protection whereby one metal corrodes in preferenceto another, thereby protecting the latter from corrosion;galvanic protection. See anodic


Asmall tapered/sloped roof area structure that helps to channelsurface water to drains; frequently located in a valley. A saddleis often constructed like a small hip roof or pyramid with adiamond-shaped base.


Abitumen of low softening point for impregnating dry felts in themanufacture of saturated roofing felts. See asphalt deadlevel and asphalt, flat


Afelt that has been immersed in hot bitumen; the felt adsorbs as muchbitumen as it can retain under the processing conditionsbut remains porous and contains voids.


Seestyrene butadiene styrene copolymer (SBS)


Inspray polyurethane foam (SPF) roof systems, shaping by grinding.


Theprocess of striking off excess concrete to bring the top surface ofthe concrete to the proper finish and elevation.


Awoven, nonwoven or knitted fabric composed of continuous strands ofmaterial used for reinforcing or strengthening membranes.


Adrainage device in the form of an outlet through a wall, parapet wallor raised roof edge typically lined with a sheet-metal sleeve.


Ahatch that provides access to the roof from the interior of thebuilding; also called a “roof hatch.”


SteelDeck Institute.


(1)A material that has the adhesive and cohesive properties to form aseal; (2) a mixture of polymers, fillers and pigments usedto fill and seal joints where moderate movement is expected; unlikecaulking, it cures to a resilient solid.


One-or two-component polyurethane foam applied as a bead and used tocontrol air leakage; for example, at deck-to-wall transitionsand/or as part of an air barrier system within the building envelope.


Acoating designed to prevent excessive absorption of finish coats intoporous surfaces; a coating designed to prevent bleeding.


Ajoint formed by mating two separate sections of material. Seams canbe made or sealed in a variety of ways, including adhesivebonding, hot-air welding, solvent welding, using adhesive tape andsealant.


Seeoverflow drainage


Amembrane that can adhere to a substrate and to itself at overlapswithout the use of an additional adhesive. The undersurfaceof a self-adhering membrane is protected by a release paper or film,which prevents the membrane from bonding toitself during shipping and handling.


Aterm used to describe materials that have the ability to adhere to avariety of surfaces when contact is promoted by applicationof pressure but that require no substances to form the bond. Seepressure-sensitive

Self-dryingroof assembly

Aterm used for an existing low-slope roof assembly that toleratessmall amounts of moisture vapor gain during times of vapordrive into the roof assembly from a building’s interior and driesdownward during times of vapor drive into the build- ing”sinterior without noticeable harm to the roof assembly’s components.

Self-dryingroof assembly

Aterm used for an existing low-slope roof assembly that toleratessmall amounts of moisture vapor gain during times of vapordrive into the roof assembly from a building’s interior and driesdownward during times of vapor drive into the build- ing’sinterior without noticeable harm to the roof assembly’s components.


Theability of a material to be applied around a penetration or at a rooftransition without the need for other flashing mate- rials.


Refersto bitumen that softens with the heat from the sun and flows to sealcracks that formed in the bitumen from other causes.


Afastener that forms receiving threads when turned in a previouslydrilled hole.


(1)An edge or edging that differs from the main part of a fabric,granule-surfaced roll roofing or cap sheet, or other mate- rial;(2) a specially defined edge of the material (lined for demarcation),which is designed for some special purpose, such asoverlapping or seaming.


Seeslip sheet


(1)The period of time a building component or system will functionsuccessfully without replacement or excessive repair assumingreasonable or expected periodic maintenance is performed; (2) thenumber of years of service a material, sys- temor structure will provide before rehabilitation or replacement isrequired.


Slightdifferences in surfacing color, such as shingle granule coloring,that may occur as a result of manufacturing opera- tions.


Theresistance to forces that cause or tend to cause two contiguous partsof a body to slide relative to each other in a directionparallel to their contact plane.


Themaximum time interval during which a material may be stored andremain in a usable condition according to the materialmanufacturer; usually related to storage conditions.


(1)A small unit of prepared roofing designed for installation withsimilar units in overlapping rows or courses on inclines normallyexceeding 3:12 slope; (2) to cover with shingles; (3) to apply anysheet material in succeeding overlapping rows likeshingles.


Adecrease in one or more dimensions of an object or material.


Anabbreviation for the International System of Units (Le SystemeInternational d’Unites).


Thecontinuous longitudinal overlap of neighboring like materials.


Afastener used to connect adjacent panels together at the side lap.


Thefinish covering of an exterior wall of a frame building; the sidingmay be a cladding material such as wood, aluminum orvinyl (but not masonry).


Anapparatus with square apertures for separating sizes of material.


Aliquid-applied elastomeric coating; the principal polymer in thedispersion contains more than 95 percent silicone resin.


Structuralprecast prestressed concrete members of a T-shaped cross-section usedas precast roof and floor deck sys- tems.

Single-component(coating or foam)

Polyurethaneor silicone material that does not require mixing of “A-component”and “B-component.”


Roofmembranes that are field-applied using just one layer of membranematerial (either homogeneous or composite) ratherthan multiple layers.


Aroof system in which the principal roof covering is a single-layerflexible thermoset or thermoplastic membrane.


SteelJoist Institute.


Thedense film portion on the surface of a liquid coating or mastic.


Functionof the time necessary to form a dense film on the surface of a liquidcoating or mastic to the extent that the ma- terialis unaffected by a water spray.

Skylight(Includes illustration)

An opening in a roof that is covered with a transparent or translucentmaterial; used to admit diffuse light to the space below; commonlymounted on a framed curb.


Alayer of reinforced concrete, generally flat and horizontal (orminimally sloped), usually of uniform thickness, placed on preparedearth or supported by beams, columns or walls.

Slabbelow grade

Aslab on grade below the elevation of the exterior earth grade. See“slab on grade.”

Slabon grade

Ahorizontal placement of concrete placed directly over a preparedearth substrate.


Ahard aggregate that is left as a residue from blast furnaces; may beused as a surfacing material on certain (typically bituminous)roof membrane systems. See blast furnace slag


Ahard, brittle metamorphic rock consisting mainly of clay mineralsused extensively as dimensional stone for steep roof- ingand in granular form as surfacing on some other roofing materials.


Sheetmaterial, such as reinforced kraft paper, rosin-size paper, polyesterscrim or polyethylene sheeting, placed between twocomponents of a roof assembly (such as between membrane andinsulation or deck) to ensure no adhesion occurs betweenthem and to prevent possible damage from chemical incompatibility,wearing or abrasion of the membrane; also calleda “separator layer” and “separator sheet.”


Relativelateral movement of adjacent components of a roof membrane. It occursmainly in roofing membranes on a slope,sometimes exposing the lower plies or even the base sheet to theweather.


Inspray polyurethane foam (SPF) roofing, a small cut about 1 inch by1/2 inch by 1/2 inch in a half-moon shape used to measurecoating film thickness.


Theangle of incline, usually expressed as a ratio of rise to run, or asan angle. See roof slope


SheetMetal and Air Conditioning Contractors’ National Association.

Smoothsurface texture

Inspray polyurethane foam (SPF) roofing, the condition of the foam inwhich the surface shows spray undulation and is idealfor receiving a protective coating.


Amembrane roof system that includes a weathering surface withoutmineral granule or aggregate surfacing.


Aseparate cap that snaps on over the vertical legs of some singlestanding or batten seam metal roof systems.


Aseries of devices attached to the roof in a pattern that attempts tohold snow in place, thus preventing sudden snow or iceslides from the roof; any device intended to prevent snow fromsliding off a roof.


Thelive load due to the weight of snow on a roof (expressed in lb/ft”2″)included in design calculations.


Theexposed undersurface of any exterior overhanging section of a roofeave.


Amanufactured or custom built air inlet source located at thedownslope eave or in the soffit of a roof assembly.


Thetemperature at which bitumen becomes soft enough to flow asdetermined using test methods defined in ASTM D36 (ring-and-ball)or D3461 (Mettler cup-and-ball).


Asanitation pipe that penetrates the roof; used to vent plumbingfixtures.


Alead and tin mixture that is melted and used to bond two pieces ofsome types of metals together.


Thepercentage by weight of the nonvolatile matter in an adhesive.


Ameasure of the extent to which a material can be dissolved in a givensolvent under specified conditions.


Anyliquid used to dissolve another material.


Aprocess where a liquid solvent is used to chemically weld or jointogether two or more layers of certain membrane mate- rials(usually thermoplastic).


Thebreaking off of plate-like pieces from a concrete, rock or masonrysurface.


Thedistance between supports or beams, girders or trusses.


Inhot-dip coatings, the crystalline structure that develops on ametallic-coated surface when the molten coating metal solidifies,especially on steel sheet and articles coated after fabrication.

Specialsteep asphalt

Seeasphalt, special steep


Aprecise statement of a set of requirements to be satisfied by amaterial, product, system or service.


Seespray polyurethane foam (SPF)


Aterm used to describe the raw materials (isocyanate and resin) usedto make spray polyurethane foam.


SprayedPolyurethane Foam Alliance; a trade association of SPF applicators,manufacturers and distributors of polyure- thanefoam, equipment and protective coatings and providers of inspections,surface preparations and other services. It is aneducational and technical resource and voice of the spraypolyurethane industry.


Bondingor joining of overlapping materials. See seam


Ametal plate placed underneath the joint between two pieces of metal.


Curedor uncured synthetic rubber tape used for splicing membranematerials.


Amembrane tear resulting from tensile stresses.


Aterm used to describe two separate concrete slabs. The first isplaced as a slab on grade or suspended slab and cov- eredwith waterproofing and a drainage system. The second slab, alsoreferred to as a topping slab, is then placed over the underlyingslab and waterproofing.


Seemopping, spot

Spraypolyurethane foam (SPF)

Afoamed plastic material, formed by mixing and spraying twocomponents, methylene diphenyl diisocynate (MDI) (“A-component”)and resin containing a polyol (“B-component”) to form a rigid,fully adhered, water-resistant and insulat- ingmembrane.


SinglePly Roofing Industry.


See“mopping, sprinkle.”


(1)A unit used in measuring roof area equivalent to 100 square feet; (2)a quantity of material sufficient to cover 100 squarefeet of a roof deck.


(1)A blade of leather or rubber set on a handle and used for spreading,pushing or wiping liquid material on, across or off asurface; (2) to smooth, wipe or treat with a squeegee.


Temporaryor permanent discoloration to the surface of a roof membrane, coatingor other covering caused by foreign materialon the surface.


Analloy of steel that contains chromium and also may contain nickel orcopper; generally, has good resistance to corro- sion.


Inmetal roofing, a type of seam between adjacent sheets of materialmade by turning up the edges of two adjacent metal panelsand then folding or interlocking them in a variety of ways.


Thefirst layer of roofing, applied along a line adjacent to thedownslope perimeter of the roof area; with steep-slope wa- ter-sheddingroof coverings, the starter course is covered by the first course.


(1)Felt, ply sheet or membrane strip that is made or cut to a widthnarrower than the standard width of the roll material andused to start the shingling pattern at a roof edge; (2) particularwidth sheet designed for perimeters in some mechani- callyattached and fully adhered single-ply systems.


Rollroofing or shingle strips applied along the downslope eave linebefore the first course of roof covering and intended to fillspaces between cutouts and joints of the first course.


Amalleable alloy of iron and carbon produced by melting and refiningpig iron and/or scrap steel; graded according to thecarbon content (in a range from 0.02 percent to 1.7 percent); otherelements, such as manganese and silicon, may be includedto provide special properties.

Steeljoist (open web steel joist)

Normallyused as a horizontal supporting member between beams or otherstructural members; suitable for the support ofsome roof decks.


Seeasphalt, steep

Steep-sloperoofs (Includes illustration)

A category of roofing that generally includes water-sheddingtypes of roof coverings installed on slopes exceeding 3:12.

Stepflashing (Includes illustration)

Individual pieces of sheet-metal material used to flash walls,around chimneys, dormers and such projections along the slope of aroof. Individual pieces are overlapped and steppedup the vertical surface.


Amethod of installing roofing rolls or sheet good materials parallelwith the slope of the roof.


(1)A measure of the load on a structural member in terms of force perunit area; (2) the force acting across a unit area in solidmaterial in resisting the tension, compression or shear that tends tobe induced by external forces; (3) the ratio of appliedload to the initial cross-sectional area.


Membraneflashing strips used for sealing or flashing metal flashing flangesinto the roof membrane.


Asphaltshingles that are manufactured in strips approximately three times aslong as they are wide with or without cut- outs.


Applicationof membrane stripping ply or plies.


Ametal roof panel designed to be applied over open framing rather thana continuous or closely spaced roof deck.

Styrenebutadiene styrene copolymer (SBS)

Highmolecular weight copolymer with thermoset and thermo-plasticproperties (thermoplastic elastomer), formed by the blockcopolymerization of styrene and butadiene monomers; used as themodifying compound in SBS polymer-modified asphaltroofing membranes to impart rubberlike qualities to the asphalt.


Thesurface upon which a roofing or waterproofing membrane is applied(e.g., in roofing, the structural deck or rigid board insulation).


Anintentional depression around a roof drain or scupper that promotesdrainage.


Ametal pan used to create a depression around a drain or scupper toenhance drainage.


Theresulting surface from the final pass of spray polyurethane foam(SPF). The following terms are used to describe the differentSPF surface textures: smooth orange peel, coarse orange peel, vergeof popcorn, popcorn, treebark and over- sprayed.


Thetop layer or layers of a roof covering specified or designed toprotect the underlying roofing from direct exposure to theweather.


Anyof several elastic substances resembling natural rubber, prepared bythe polymerization of butadiene, isoprene and otherunsaturated hydrocarbons. Synthetic rubber is widely used in thefabrication of single-ply roofing membranes.


Thecondition created by the overlapping intersection of three or foursheets in the membrane; also termed a “T-joint.”


Asection of the exposed portion of a strip shingle defined by cutouts.


Inspray polyurethane foam (SPF) roofing, a curing phase of polyurethanefoam when the material is no longer sticky. Whenthe polyurethane foam is tack-free, it can be sprayed over withanother pass, referred to as a “lift.” With some care, thepolyurethane foam can be walked on soon after it is tack-free. Seelift


Whitishpowder applied at the factory to the surface of some roofingmaterials (e.g., vulcanized EPDM membranes), used asa release agent to prevent adhesion of the membrane to itself. Talcis a naturally occurring mineral.


Asystem of precut or premolded insulation boards or a pouredinsulation fill designed to provide slope to the roof deck beforeinstalling the roof membrane.


(1)The technique of connecting joints between insulation boards or deckpanels with tape; (2) the technique of using self-adheringtape-like materials to seam or splice single-ply membranes.


Abrown or black bituminous material, liquid or semisolid inconsistency in which the predominating constituents are bitu- mensobtained as condensates in the processing of coal, petroleum,oil-shale, wood or other organic materials.


Theload required to tear a material when the stress is concentrated on asmall area of the material by the introduction of aprescribed flaw or notch.


Themaximum force required to tear a specimen.


Thestrength of a material under tension as distinct from torsion,compression or shear.


Thetreatment or method of anchoring and/or sealing the free edges of amembrane in a roof or waterproofing system.


Analloy of lead and tin used to coat sheets of carbon steel orstainless steel for use as metal roofing sheet.


See“core cut.”


Adefinitive procedure for the identification, measurement andevaluation of one or more qualities, characteristics or prop- ertiesof a material, product, system or service that produces a testresult.

Texturalslate roof system

Aterm used to designate a slate roof system with a range of slatethicknesses mixed throughout; usually uses slates with roughertexture than standard slate with uneven tails or butts.


Intorched membrane applications over combustible substrates, anabove-deck barrier incorporated into a roof system beforetorching as a fire-safety practice. Acceptable thermal barriersinclude: minimum 3/4-inch-thick perlite board insula- tion,minimum 3/4-inch-thick fiberglass or mineral wool board insulation,or minimum 1/4-inch-thick glass-faced gypsum board.

Thermalconductance (C)

Thetime rate of steady-state heat flow through a unit area of a materialor construction induced by a unit temperature differencebetween the body surfaces. In English (inch•pound) units ofmeasurement, the number of Btu that pass through aspecified thickness of a one-square-foot sample of material in onehour with a temperature difference between the two surfacesis 1 degree Fahrenheit. In English (inch•pound) units, it isexpressed as Btu/h•ft”2″•F.” Note 1: A thermal conduc- tance(C) value applies to a specific thickness of a specific material.”“ Note 2: It is mathematically incorrect to multiply ordivide the thermal conductance (C) value for a specific thickness ofa material to determine the thermal conductance valueof a different thickness of the same material.” “ Note 3: It ismathematically incorrect to add thermal conductance (C)values to determine overall thermal performance. If it is necessaryto determine the overall thermal performance of a construction,it is appropriate to convert the individual thermal conductance (C)values to thermal resistance (R) values (i.e.,R = 1/C) and then add the thermal resistance values (i.e., R”t” =R”1″ + R”2″ + …).”

Thermalconductivity (k)

Thetime rate of steady state heat flow through a unit area of ahomogeneous material induced by a unit temperature gra- dientin a direction perpendicular to that unit area. In English(inch•pound) units of measurement, it is the number of Btu thatpass through a 1-inch thickness of a 1-square-foot sample of materialin one hour with a temperature difference be- tweenthe two surfaces of 1 degree Fahrenheit. In English (inch•pound)units, it is expressed as Btu•inch/h•ft”2″•F.” Note 1: Athermal conductivity (k) value applies to 1-inch thickness of aspecific material.” “ Note 2: It is mathematically incorrect toadd, multiply or divide the thermal conductivity (k) value of amaterial to determine the thermal performance value of a differentthickness of the same material. If it is necessary to determine thethermal performance of a specific thickness of amaterial, it is appropriate to convert the thermal conductivity (k)of the material to a thermal resistance (R) value (i.e., R = 1/k)and then perform the mathematical calculation.”


Afluctuation in material, system component or system stress mode, suchas a change from tension to compression and backto tension, and any related displacements caused by recurringtemperature fluctuations.


Theincrease in the dimension or volume of a body because of temperaturevariations.


Amaterial applied to reduce the flow of heat.


Changesin dimension of a material as a result of temperature changes.

Thermalresistance (R)

Thequantity determined by the temperature difference at steady statebetween two defined surfaces of a material or con- structionthat induces a unit heat flow rate through a unit area. In English(inch•pound) units, it is expressed as F•ft”2″•h/ Btu.”Note 1: A thermal resistance (R) value applies to a specificthickness of a material or construction.” “ Note 2: The thermalresistance (R) of a material is the reciprocal of the thermalconductance (C) of the same material (i.e., R = 1/C).” Note3: Thermal resistance (R) values can be added, subtracted, multipliedand divided by mathematically appropriate methods.”


Thestress-producing phenomenon resulting from sudden temperature changesin a roof membrane when, for example, a coldrain shower follows brilliant sunshine.


Stressintroduced by uniform or nonuniform temperature change in a structureor material that is contained against ex- pansionor contraction.

Thermaltransmittance (U or U-factor)

Theheat transmission in unit time through unit area of a material orconstruction and the boundary air films induced byunit temperature difference between the environments on each side. InEnglish (inch•pound) units, it is expressed as Btu/h•ft”2″•F.”Note 1: A thermal transmittance (U) value applies to the overallthermal performance of a system (e.g., roof assembly).”“ Note 2: Thermal transmittance (U) is sometimes called the overallcoefficient of heat transfer.” “ Note 3: Thermaltransmittance (U) is the reciprocal of the overall thermal resistance(R”t”) of a system (i.e., U = 1/R”t”).”


Amaterial that softens when heated and hardens when cooled. Thisprocess can be repeated provided the material is not heatedabove the point at which decomposition occurs.


Amaterial having the general properties of an elastomer and capable ofbeing repeatedly softened by heat and hardened toshape by cooling without significant degradation of the polymersystem; typically more thermally and pressure-sensitive andmore sensitive to solvents than thermoset elastomers.

Thermoplasticolefin membrane (TPO)

Ablend of polypropylene and ethylene-propylene polymers, colorant,flame retardants, ultraviolet radiation absorbers and otherproprietary substances that may be blended with the TPO to achievethe desired physical properties. The membrane mayor may not be reinforced.


Aclass of polymers that when cured using heat, chemical or other meanschange into a substantially infusible and insolu- blematerial.


(1)A volatile liquid added to an adhesive or coating material to modifythe consistency or other properties; (2) a liquid usedto clean equipment or other surfaces.


Awater-resistant membrane or material assembly extending totallythrough a wall and its cavities positioned to direct waterwithin the wall to the exterior, usually through weep holes.


Thenut and bolt assembly attached to the tie-back rod, which stabilizesthe shoring or lagging.


Inroofing and waterproofing, the transitional seal used to terminate aroofing or waterproofing application at the top or bottomof flashings or by forming a watertight seal with the substrate,membrane, or adjacent roof or waterproofing sys- tem.


Abolt having a nut with pivoted, flanged wings that close against aspring when it is pushed through a hole and open after emergingfrom the hole; used to fasten objects to a hollow wall or to a wallthat is accessible only from one side.


Oneof the oldest types of dimensional structural wood used as roofdecking. The sides are cut with convex and concave groovesso adjacent planks may join in alignment with each other to form auniform roof deck.


See“wear course.”


Methodused in the installation of polymer-modified bitumen membranescharacterized by using open flame propane torchequipment.




Inwaterproofing, a membrane formulated to withstand a predeterminedamount of pedestrian or vehicular traffic with separateprotection and a wear course.

Treebarksurface texture

Inspray polyurethane foam (SPF) roofing, the surface condition of thefoam that shows a coarse texture where valleys formsharp angles. This surface is unacceptable for proper coating andprotection.


TileRoofing Institute; originally founded in 1971 as the National TileRoofing Manufacturers Association (NTRMA); also wasthe Roof Tile Institute (RTI).


Astructure made up of three or more members usually in some triangulararrangement with each member designed to carrya tension or compression force. The entire structure in turn acts asa beam.


Theprocess of removing deteriorated mortar from an existing masonryjoint and troweling new mortar or other filler into thejoint.


Inspray polyurethane foam (SPF) roofing, a coating of polyurethane foamformed by the mixing and reaction of two differ- entmaterials.


SeeUnderwriters Laboratories Inc. (UL)


Anidentification label or seal affixed to a roofing product or packagewith the authorization of Underwriters Laboratories Inc.The presence of the label indicates the product has met certainperformance criteria.


Invisibleelectromagnetic radiation adjacent to the violet end of the visiblespectrum with wavelengths from about 200 to 400nm (nanometers [1 nm = 1×10″-9″ m]).


Anasphalt-saturated felt or other sheet material (may be self-adhering)installed between a roof deck and roof covering, usuallyused in a steep-slope roof construction. Underlayment is primarilyused to separate a roof covering from the roof deck,shed water and provide secondary weather protection for the roof areaof the building.

UnderwritersLaboratories Inc. (UL)

Anindependent product safety certification organization that testsproducts and writes standards for safety worldwide. ULtests, rates and classifies roof assemblies for their resistances tofire, impact, leakage, corrosion of metal components andwind uplift.


(1)Unusual situation not reasonably anticipated based on contractdocuments; (2) unknown physical condition of an unusualnature that differs materially from those ordinarily encountered.


Seewind uplift




Damagedone by the ultraviolet rays of the sun.

Valley(Includes illustration)

The internal angle formed by the intersection of two slop- ingroof planes.


Seevapor retarder


Themovement of water vapor from a region of high vapor pressure to aregion of lower vapor pressure.


Thepressure exerted by a vapor of a solid or liquid when in equilibriumwith the liquid or solid.


Layer(s)of material or a laminate used to appreciably reduce the flow ofwater vapor into a roof assembly.


(1)A single wythe of masonry for facing purposes that may not bestructurally connected; (2) any of the thin layers of woodglued together to form plywood.


Anopening designed to convey air, heat, water vapor or other gas frominside a building or a building component to the atmosphere.


Inspray polyurethane foam (SPF) roofing, the verge-of-popcorn surfacetexture is the roughest texture suitable for re- ceivingthe protective coating on an SPF roof. The surface shows a texturewhere nodules are larger than valleys with the valleysrelatively cured. This surface is acceptable for receiving aprotective coating only because of the relatively cured valleys.However, the surface is considered undesirable because of theadditional amount of coating material required to protectthe surface properly.


Anaggregate used in lightweight insulating concrete formed by heatingand expanding a micaceous material.


Theresistance of a material to flow under stress. For bitumen, viscositymeasurements are reported in centipoise (cP or cPs)at a specific temperature; as viscosity increases, flow ratedecreases.


Resistantto flow under stress. See equiviscous temperature (EVT)


Anopen space or break in consistency.


Arelative term expressing the tendency to form vapor.


Structurallyreinforced concrete roof deck construction cast with wafflelikearrangements of perpendicular ribs on the ceil- ingside. Standard configurations include 6-inch-wide ribs on 36-inchcenters cast using square 30-inch forms and 5-inch- wideribs on 24-inch centers formed using square 19-inch forms.


(1)High traffic and high-service-frequency areas on a rooftop,particularly those leading and adjacent to vents, hatches andheavy duty air-conditioning units; (2) materials or accessories suchas traffic mats or pavers installed on rooftop sur- facesto provide wearing surfaces for traffic and/or protect a roof systemfrom damage resulting from rooftop traffic.


Aprimer typically provided on the back side of painted metal productsto help protect the underlying metal from wear and corrosion.

Waterand ice-dam protection membrane (Includes illustration)

A continuous membrane installed under steep-slope roof- ingmaterials in areas subject to ice damming or wind-driven rain thatprohibits water that gets through the roof covering fromgetting into the structure; ice- and water-protection membranesclassified by ASTM D1970 must also seal around fasteners.




Thelevel within the ground below which the soil is saturated with water.


Aflood test (often minimum 24 hour) or flowing-water test to evaluatethe watertight integrity of a waterproofing system (nota damp-proofing system) under hydrostatic (standing water) ornonhydrostatic (flowing water) conditions. See flood testand flowing-water test

Watervapor pressure

Thepressure of water vapor at a given temperature; the component ofatmospheric pressure contributed by the presence ofwater vapor. See “vapor pressure.”

Watervapor transmission

Ameasure of the rate of transmission of water vapor through a materialunder controlled laboratory conditions of tem- peratureand humidity. Customary units are grains/h•ft”2″. See “watervapor diffusion.”


Theability of individual, overlapping components to resist the passageof water without hydrostatic pressure.

Water-sheddingroof system

Aroof system that depends on gravity for quick drainage via watershedding to prevent water entry into or through the sys- tem.


Thequality of a membrane, membrane material or other component toprevent water entry.


Treatmentof a surface or structure to prevent the passage of water underhydrostatic pressure.


Anassembly of interacting waterproofing components including the deck,membrane and protection/drainage/insulation course.


Thepart of a waterproofing system that has the primary function ofexcluding water; it does not include accessories such asdrainage materials or protection boards. See membrane


Asystem of interacting waterproofing components consisting at aminimum of a membrane but may also include protec- tion,drainage and insulation courses, as well as waterstops, expansion andcontrol joints, various flashings and counter- flashings,and overburden such as pavers, cast concrete and wire mesh or rebars.It does not include the substrate.


Adiaphragm used across a joint as a sealant usually to prevent thepassage of water.


Theability of a membrane or roof covering to prevent the passage ofwater with a limited amount of hydrostatic pressure.


Tojoin pieces of material together by heat fusion.


Acondition in which free water is present in a substance.

Wetfilm gauge

Agauge for measuring the thickness of wet coating as applied to a flatsmooth surface.

Wetfilm thickness

Thethickness, expressed in mils, of a coating or mastic as applied butnot cured. For comparison, see dry film thickness


Theprocess of moisture movement by capillary action.


Inspray polyurethane foam (SPF) roofing, a device to keep the SPF fromdrifting or being blown away by the wind from the sprayarea.


Theforce caused by the deflection of wind at roof edges, roof peaks orobstructions causing a drop in air pressure imme- diatelyabove the roof surface.


Amethod of valley construction in which shingles or roofing from bothsides of the valley extend across the valley and are woventogether by overlapping alternate courses as they are applied.


Inspray polyurethane foam (SPF) roofing, the volume of foam per unitweight normally expressed as board feet per pound orboard feet per 1,000 pounds.


Asoft, self-healing metal that reacts with the environment to producea soft blue-gray zinc carbonate patina that protects theunderlying metal from corrosion. Zinc is commonly used as sacrificial(galvanized) coating for a base metal such as sheetsteel and iron, in various metal alloys and in oxide form as a whitepigment.