Glossary of Terms

Common to the Spray

Polyurethane Foam

Industry

Spray Polyurethane Foam AllianceCopyright 1994

To order copies of this publication, call 800-523-6154 and request SPFA Stock Number AY-119Revised6/04

The Building Envelope & Technical Committee’s of the Spray Polyurethane Foam Alliance offer thisinformation as an industry service.

TECHNICAL COMMITTEE

Roger Morrison, Chairman Robert SmithNorth Caolina Foam Industries KoSa

Jim Calkins John StahlDow Chemical Preferred Solutions, Inc.

Brad Beauchamp Dennis VandewaterStepan Co. Sadler Coatings Systems

Mary Bogdan Laverne Dalgeish- Ad HocHoneywell CUCFA

John Courier E quipment &Coatings

John Ewell

Dallas/Ft. Worth Urethane, Inc.

John Hatfield

Penta Engineering Group, Inc.

Tim Leonard

ERSystems

Jack Moore

West Roofing Systems, Inc.

Bruce Schenke

BASF

Larry Smiley Poly-Tek.

This brochure was developed to aid specifiers in choosing spray-applied polyurethane foam systems. Theinformation provided herein, based on current customs and practices of the trade, is offered in good faith andbelieved to be true, but is made WITHOUT WARRANTY, EITHER EXPRESSED OR IMPLIED, AS TOFITNESS, MERCHANTABILITY, OR ANY OTHER MATTER. SPFA DISCLAIMS ALL LIABILITYFOR ANY LOSS OR DAMAGE ARISING OUT OF ITS USE. Individual manufacturers and contractors should beconsulted for specific information. Nominal values which may be provided herein are believed to be representative,but are not to be used as specifications nor assumed to be identical to finished products. SPFA does notendorse the proprietary products or processes of any individual manufacturer, or the services of any individualcontractor.

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AA-SIDE: (A-Component) One component of a twocomponent system. For polyurethane foam andcoatings the isocyanate component. (SeeISOCYANATE)

ABSOLUTE HUMIDITY: The actualconcentration of water vapor in air. May beexpressed in units of kPa, grains of moisture perpound of dry air, pounds of moisture per pound ofdry air, or as a partial pressure as inches of mercury(in. Hg).

ACCELERATOR: A chemical additive tocoating or polyurethane foam systems used inrelatively small amounts to increase the speed of thereaction or decrease the time required to cure or dry.

ACRYLIC COATING: A coating system based onan acrylic resin. Generally, a “water based” coatingsystem which cures by coalescence and air-drying.

ACRYLICS: Resins resulting from thepolymerization of derivatives of acrylic acids,including esters of acrylic acid, methacrylic acid,acrylonitrile, and their copolymers. They can becarried in a water or solvent solution and they arefilm-forming materials.

ADHESION: The degree of attachment orbonding of one substance to another. The degree ofattachment or bonding between applications of thesame substance. (For comparison, see also:COHESION)

AGGREGATE: Any mineral surfacing material.May include crushed gravel, river washed gravel,roofing granules, etc.

AGING: The effect on materials that are exposedto an environment for an interval of time.

AIR BARRIER: A material which is applied inconjunction with a building component (such as awall, ceiling or sill plate) to prevent the movementof air through that component.

AIR BARRIER SYSTEM: The assembly ofcomponents used in building construction to createa plane of air tightness throughout the buildingenvelope and to control air leakage.

AIR EXFILTRATION: Air passing from theconditioned interior of a building to the exterior.

AIR INFILTRATION: Exterior air passing intothe conditioned area of a building.

AIR LEAKAGE: The uncontrolled flow ofconditioned air through gaps, cracks or holes in thebuilding envelope or its components.

ALIPHATIC (POLYURETHANE): An organicpolymer containing straight or branched chainarrangements of carbon atoms. As compared toaromatic urethanes, coatings based on aliphaticurethanes usually have better gloss, color retention,and weathering.

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ALLIGATORING: Pattern cracking of a coatingor mastic. So called because of its resemblance tothe pattern of an alligator skin. (See CHECKING)

AMBIENT TEMPERATURE: The surroundingair temperature.

APPLICATION RATE: The quantity (mass,volume, or thickness) of material applied per unitarea.

AREA DIVIDER: A raised, flashed assembly(typically a single or double wood member attachedto a wood base plate) that is anchored to the roofdeck. It is used to relieve thermal stresses in a roofsystem where an expansion joint is not required, orto separate large roof areas (sometimes betweenexpansion joints), and may be used to facilitateinstallation of tapered insulation.

AROMATIC (POLYURETHANE): An organicpolymer usually containing one or more benzenerings structures. Coatings are usually tougher andat a lower cost than aliphatics. As compared toaliphatic, coatings based on aromatic polyurethane'susually have tougher physical properties and costless.

AROMATIC SOLVENTS: Hydrocarbon solventscomprised of organic compounds, which contain anunsaturated ring of carbon atoms, includingbenzene, xylene, toluene and their derivatives.

ASPHALT: A dark brown to black bituminoussubstance, solid or semi-solid in consistency,obtained from petroleum refining. It consists mainlyof hydrocarbons. Asphalt products are available for

hot or cold application. Asphalt will dissolve inmineral spirits.

ASTM: American Society for Testing andMaterials. A test standards development agency.

ATOMIZATION: The break up of liquid or fluidinto spray when forced through a small opening ororifice at high pressure.

BB-SIDE: (B-component) One component of a twocomponent system. For polyurethane foam andcoatings the resin component. (See RESIN)

BACK ROLLING: Rolling wet coating behind aspray or roller application to insure better coverageon rough surfaces.

BASE COAT: The first coat of a multi-coatsystem. This should be applied the same day as thespray polyurethane foam.

BIRDBATH: Random, inconsequential amounts ofresidual water on a roof membrane.

BITUMEN: A class of amorphous, dark brown toblack (solid, semi-solid, or viscous), high molecularweight hydrocarbons derived from petroleumrefining (asphalt) or coal reduction (coal tar).

BLEEDING: (1) The diffusion of coloring matterthrough a coating from its substrate (such asbleeding of asphalt mastic through coating). (2) The

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absorption of oil or vehicle from a compound intoan adjacent porous surface.

BLISTER: An uplifting of coating orpolyurethane foam caused by an enclosed pocket ofgas or liquid entrapped between coating passes,foam and coating, foam and substrate, or within thefoam itself. Caused by the DELAMINATION (seealso) of one or two components in an insulation orroofing system.

BLOWING AGENT: A gas or a substance capableof producing a gas used in making foamedmaterials.

BLOWHOLES: Holes in the coating and/orpolyurethane foam surface caused by escaping gasthat was produced during the foaming application.

BOCA: Building Officials and CodeAdministrators, International. One of the threemodel building codes in the U. S.

BOND, CHEMICAL: Adhesion between surfaces,usually of similar materials, resulting from achemical reaction or cross linking of polymerchains.

BOND, MECHANICAL: Adhesion betweensurfaces resulting from interfacial forces or aphysical interlocking.

BUILDING CODE: A system of principles orrules governing the design and construction ofbuildings. Local governments generally adopt or

modify one of the national model building codes.(See BOCA, ICBO, IBC, SBCCI)

BUILDING ENVELOPE: The exterior shell of abuilding designed for energy conservation andweather protection.

BUILDING SCIENCE: Involves the applicationof basic science knowledge and analysis proceduresto the design of buildings. There is a specialknowledge and experience required, and suchexpertise is also beneficial in determining how tocorrect problems in existing buildings and toexplain what went wrong to cause the problem.

BUR: (See BUILT-UP ROOF)

BUILT-UP ROOF: A roofing membraneconsisting of alternating applications of bituminousimpregnated felts (or fabrics) and hot (or cold)mopped bitumen. The membrane is generallysurfaced with aggregate.

BUTYL COATING: An elastomeric coatingsystem derived from polymerized isobutylene.Butyl coatings are characterized by low water vaporpermeability.

CCABO: Council of American Building Officials.A code agency.

CALORIMETER: An apparatus for measuringquantities of heat developed by combustion.

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CANT: A beveling of polyurethane foam at a rightangle joint for strength and water run off.

CANT STRIP: A beveled strip used underflashings to modify the angle at the point where theroofing or waterproofing membrane meets anyvertical element.

CAP FLASHING: Usually composed of metal,used to cover or shield the upper edges of themembrane base flashing, wall flashing or primaryflashing.

CAPACITANCE METER: A device used todetect moisture or wet materials within a roofsystem by measuring the ratio of the change to thepotential difference between two conductingelements separated by a nonconductor.

CAPILLARY ACTION, CAPILLARITY: Themovement of liquid in the interstices of insulationor other porous material as a result of surfacetension.

CATALYST: An ingredient in a coating orpolyurethane foam system which initiates achemical reaction or increases the rate of a chemicalreaction.

CAULK: A flexible waterproofing material usedto seal cracks, seams, or small breaks in awaterproofing or an air seal system. Usuallysupplied in tubes and applied with a caulking gun.(See: SEALANT)

CAVITATION: The vaporization of a liquidunder the suction force of a pump. Usually due toinadequate flow to a pump; the vaporization cancreate voids within the pump or the pump supplyline. In polyurethane foam spray pumps, cavitationwill result in OFF-RATIO FOAM (see also).

CAVITY WALL: An exterior wall, usually ofmasonry, consisting of an outer and inner widthseparated by a continuous air space.

CELLULAR: Describes a composition of plasticor rubber with relative density decreased by thepresence of cells dispersed throughout its mass. Inclosed-cell materials, the cells are predominatelyseparate from each other. In open-cell materials,the cells are predominately interconnected.

CENTIPOISE: (cps) A unit of measure ofabsolute viscosity. (Note: The viscosity of water isone centipoise. The lower the number, the less theviscosity.)

CHALKING: The formation on a surface of apowdery substance due to weathering.

CHECKING: A defect in a coated surfacecharacterized by the appearance of fine fissures inall directions. Designated as “surface checking” ifsuperficial, or “through checking” if extendingdeeply into the coating or to an adjoining surface.

CHEMICAL BOND: See BOND, CHEMICAL

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CHEMICAL RESISTANCE: The ability towithstand contact with specified chemicals withouta significant change in properties.

CHLORINATED RUBBER: Resin formed by thereaction of rubber and chlorine to form a coating(i.e. primer or Hypalon ) or single ply membrane.

COAL TAR: A dark brown to black hydrocarbonobtained from the destructive distillation of coal.Used in built-up roofs or in below gradeconstruction as a waterproofing agent. Coal tarwhen mixed with mineral spirits will produce ayellow-green to amber color, but will not dissolve.

COALESCENCE: The formation of a film ofresinous or polymeric material when waterevaporates from an emulsion or latex system,permitting contact and fusion of adjacent latexparticles. Action of the joining of particles into afilm as the volatile evaporates.

COARSE ORANGE PEEL SURFACETEXTURE: A surface showing a texture wherenodules and valleys are approximately the same sizeand shape. This surface is acceptable for receivinga protective coating because of the roundness of thenodules and valleys.

COATING: A layer of material applied over asurface for protection or decoration. Coatings forpolyurethane foam are liquids, semi-liquids, ormastics; spray, roller, or brush applied; and areelastomeric. (See ELASTOMERIC)

COBWEBBING: Production of fine filamentsinstead of the normal atomized particles when somecoatings are sprayed.

COEFFICIENT OF THERMAL EXPANSION:A mathematical formulation used to predict thechange in dimension (typically length) of a materialas a function of temperature change.

COHESION: The degree of internal bonding ofone substance to itself. (See ADHESION)

COLD APPLIED: Capable of being appliedwithout heating as contrasted to hot-applied. Cold-applied products are furnished in a liquid state,whereas hot-applied products are furnished as solidsthat must be heated to liquefy them.

COLLECTOR BOX: (See CONDUCTORHEAD)

COLLOIDAL DISPERSION: A mixture whereina finely divided material is uniformly distributedwithin a liquid. Latex emulsion is a colloidaldispersion of resin in water. (See LATEX)

COLOR STABILITY: The ability to retain theoriginal color without significant change over time.

COMBUSTIBLE: Capable of burning.

COMPARATOR: An eyepiece withmagnification ranging from 4-12 power, with ascale used for measuring thickness.

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COMPATIBLE MATERIALS: Two or moresubstances that can be mixed, blended, or attachedwithout separating, reacting, or affecting thematerials adversely.

COMPRESSIVE STRENGTH: The stress orforce applied parallel to the direction of thepolyurethane foam rise at 10% deformation or atyield point.

CONDENSATE: The liquid resulting from theCONDENSATION (see also) of a gas or vapor.

CONDENSATION: The action of a vaporconverting into a liquid.

CONDITIONING: The exposure of a material tothe influence of a prescribed atmosphere for astipulated period of time or until a stipulatedrelation is reached between material andatmosphere.

CONDUCTOR HEAD: A transition componentbetween a through-wall scupper and downspout tocollect and direct run-off water.

CONTROL JOINT: (See AREA DIVIDER)

COPING: The covering at the top of a wall orparapet designed to shed water.

COPOLYMER: A polymer consisting ofmolecules containing large numbers of units two ormore chemically different types in irregularsequence.

CORE SAMPLE: The actual material of a crosssection of the roofing material, insulation, etc.showing the various layers.

COUNTERFLASHING: Formed metal orelastomeric sheeting secured on or into a wall, curb,pipe, roof-top unit, or other surface to cover andprotect the upper edge of a base flashing and itsassociated fasteners.

COVERAGE: The unit quantity of materialnecessary to apply to achieve a desired thickness.Usually expressed in (square feet per gallon) squaremeter per liter or (gallons per hundred square feet)liters per square meter.

CRAZING, CRAZE CRACKS: Fine, randomcracks in forming a network on the surface of acoating or film.

CREAM TIME: The time, measured in seconds ata given temperature, when the polyurethane foamcomponents will begin to expand after being mixed.

CREEP: (1) The permanent deformation of amaterial caused by slow movement over timeresulting from thermal or load stresses. (2) Lateralmovement of expanding foam.

CRICKET: A relatively small, elevated areadesigned to facilitate the flow of water around anobstruction on a roof such as a chimney or skylight.

CROSS HATCH: An application method forliquid applied materials whereby successive layers

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or passes are applied at 90° to the previousapplication.

CROSSOVER: An undesirable mixing of iso andresin components as a result of unbalancedpressures at the spray gun. May result in anequipment blockage.

CURE: The chemical and physical changes in asubstance which result in achieving the desired,final characteristics of the substance.

CURE TIME: The time required to effect curing.The time required for a material to reach its desired,long-term characteristics.

CURING AGENT: An agent in a coating oradhesive that increases the rate of cure.

CURTAIN WALL: A lightweight exterior wallsystem supporting no more than its own weight, theroof and floors being carried by an independentstructural framework.

DDEAD LEVEL: Absolutely horizontal, or zeroslope.

DEAD LOADS: The weight imposed on astructural roofing system, including thewaterproofing system, roof mounted equipment,roof structural members, and anything hung fromthe roof structure.

DECK: The structural surface to which theroofing or water proofing system (includinginsulation) is applied.

DEFLECTION: The deviation of a structuralelement from its original shape or plan due tophysical loading, temperature gradients, ormovement of its support.

DEGRADATION: The deterioration of asubstance caused by contact with its environment.

DELAMINATION: The separation of layerswithin a material or materials. May result inBLISTER (see also) formation.

DESSICANT: A drying agent.

DEW POINT: The temperature at which a vaporbegins to condense.

DIFFUSION: The movement of water vapor fromregions of high concentration (high water vaporpressure) toward regions of lower concentration(due to random thermal motion).

DIISOCYANATE: An organic chemicalcompound having two reactive isocyanate(-N=C=O) groups; used in the production ofpolyurethane foams and coatings.

DIMENSIONAL STABILITY: The ability of amaterial to retain its original size and shape. Forpolyurethane foam, dimensional stability isdetermined over time under conditions of controlled

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temperature and humidity. Measured as a percentof original dimension.

DISCOLORATION: Any change from the initialcolor. (See COLOR STABILITY)

DRAINAGE: (See POSITIVE DRAINAGE)

DRIP EDGE: A projecting piece of materialshaped to throw off water and prevent its runningdown the face of the wall or other surface.

DRY BULB TEMPERATURE: The temperatureof air as measured by an ordinary thermometer.(See AMBIENT TEMPERATURE)

DRYING TIME: The time required for thematerial to become tack free and will no longer beadversely affected by weather phenomena such asdew, rain, or freezing. (Contrast with, CURETIME).

E

ELASTOMER: A material which at roomtemperature is capable of being stretched repeatedlyat least twice its original length 100% elongationand, upon release of stress, will return to its originaldimensions. (See ELONGATION)

ELASTOMERIC: The elastic, rubber-likeproperties of a material that will stretch when pulledand will return relatively quickly to its originalshape when released.

ELASTOMERIC COATING: A coating systemwhich, when fully cured, is capable of beingstretched at least twice its original length (100%elongation) and recovering to its originaldimensions. (See ELONGATION)

ELONGATED CELLS: Excessively large cells infoam or coating generally caused by off-ratiomaterials, moisture contamination, or excessiveheat.

ELONGATION: The increase in length of aspecimen at the instant that rupture occurs(expressed as a percent of the original length).

EMISSIVITY: The ability of a material to radiateor absorb radiant energy.

EMULSION: A colloidal dispersion of one liquidin another. (See LATEX; COLLOIDALDISPERSION)

EPOXY: A class of synthetic, thermosettingresins, which produce tough, hard, chemical-resistant coatings and adhesives.

EXOTHERM: Heat generated by a chemicalreaction.

EXPANSION JOINT: A joint designed toaccommodate movement in the structure orcomponents of the system due to thermal or stress-load variation.

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F

FAST SET: A coating system with a very fastinitial cure time, usually five seconds to one hour.

FEATHERED EDGE: The thin tapered outsideedge of a polyurethane foam pass.

FELTS: A flexible sheet manufactured by theinterlocking of fibers through a combination ofmechanical work, moisture, and heat. Roofing feltsmay be manufactured principally from wood pulpand vegetable fibers (organic felts), asbestos fibers(asbestos felts), glass fibers (fiberglass felts or plysheet), or polyester fibers.

FERROUS METAL: An iron compound, i.e.,steel, cast iron, or galvanized steel. As a rule ofthumb, most ferrous metals are magnetic.

FILLER: A relatively inert ingredient added tocoating or polyurethane foam formulations tomodify physical characteristics.

FILM THICKNESS: The thickness of amembrane or coating. Wet film thickness is thethickness of a coating as applied; dry film thicknessis the thickness after curing. Film thickness isusually expressed in mm/mils (thousandths of aninch).

FIRE RESISTANCE: The ability of a buildingcomponent to resist the spread of fire.

FISHEYE: Coating defect that manifests itself bythe separation of wet coating into a recognizedpattern resembling small “dimples” or “fish eyes”.

FISHMOUTH: (Also referred to as an EdgeWrinkle) 1) A half-cylindrical or half-conicalshaped opening or void in a lapped edge or seam,usually caused by wrinkling or shifting of ply sheetsduring installation; 2) In shingles a half-conicalopening formed at a cut edge.

FLAME-RETARDANT: A substance which isadded to a coating or polyurethane foamformulation to reduce or retard its tendency to burn.

FLAME SPREAD: Per ASTM E-84, a measure ofrelative combustibility. The flame spread of a testedmaterial is rated relative to asbestos cement board(flame spread = 0) and red oak flooring (flamespread = 100).

FLAMMABILITY: Relative ability of a materialto support combustion as expressed by its flashpoint.

FLASH COAT: A thin initial pass of a spray-applied material.

FLASH POINT: The lowest temperature of amaterial at which it gives off vapors sufficient toform an ignitable mixture with air near its surface.

FLASHING: The portion of a roof system used towaterproof at termination’s or vertical surfaces.

FLUOROCARBONS: Components used asblowing agents.

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FLUTES: The grooves in the lower section ofmetal decking that give it added strength.

FM: Factory Mutual. An independent testingagency.

FMRC: Factory Mutual Research Corporation. Apart of FM.

FOAM STOP: The roof edge treatment uponwhich polyurethane foam is terminated.

FREEZE THAW CYCLE: The freezing andsubsequent thawing of material.

FRIABILITY: The tendency of a material orproduct to crumble or break into small pieces easily.

FROTH PACK: Pressurized containers ofpolyurethane foam components.

GGLASS EYES OR GLASS WINDOWS: A thinclear membrane that forms over elongatedpolyurethane foam cells. Glass eyes may breakwhen coated, forming a pinhole.

GLOSS: The shine, sheen, or luster of a driedfilm.

GRANULE: Size No. 11 ceramic aggregateembedded into wet coating over polyurethane foamfor aesthetics, traction, and mechanical resistance.

GRAVEL STOP: The roof edge treatmentdesigned to retain gravel.

H

HARDNESS: Ability of a coating film, as distinctfrom its substrate, to resist cutting, indentation, orpenetration by a hard object.

HCFC: Hydrochloroflourocarbon. A secondgeneration blowing agent for polyurethane foam.

HEAT AGING: Controlled exposure of materialsto elevated temperatures for a period of time.

HEAT SINK: A cold substrate that absorbs theSPF exothermic heat, slowing down the reactionand / or rise of the polyurethane foam or coating.

HFC: Hydrofluorocarbon. A possible thirdgeneration blowing agent for SPF.

HIDING POWER: The ability of a coating to hideor obscure a surface to which it has been uniformlyapplied.

HOLIDAYS: Application defects whereby smallareas are left uncoated.

HYDROPHILIC: Having an affinity orattraction for water; having the ability of unitingwith or dissolving in water. “Water loving”.

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HYDROPHOBIC: Having no affinity for water;not compatible with water. “Water fearing”.

HYGROSCOPIC: Attracting, absorbing, andretaining atmospheric moisture.

HYGROSCOPICITY: The capacity of acompound or substance to absorb water.

IIBC: International Building Code.

ICAA: Insulation Contractors Association ofAmerica.

ICBO: International Conference of BuildingOfficials. One of the model building codes in theU.S.

ICC: International Code Council. Recently formedto publish a common and single code to replaceSBCCI, BOCA, and ICBO which will be called theInternational Building Code Council (IBC).

IGNITION TEMPERATURE: The minimumtemperature to which a solid, liquid, or gas must beheated in order to initiate or cause self-sustainedcombustion independent of the heating element.

IMPACT RESISTANCE: Ability to withstandmechanical or physical blows without the loss ofprotective properties. The impact resistance of theroofing assembly is a function of all its componentsnot just the membrane itself.

INTERLAMINAR ADHESION: Adhesionbetween polyurethane foam passes or coatingpasses.

ISO: Short for isocyanate.

ISOCYANATE: A highly reactive organicchemical containing one or more isocyanate(-N=C=O) groups. A basic component inpolyurethane foam chemical systems and somepolyurethane coating systems.

Kk-FACTOR: Thermal conductivity for a unitthickness of material. Expressed as W/m•°K(Btu•in/hr•ft2•°F). R-VALUE (see also) is equal tothe thickness of the material divided by the k-factor(R = x/k where x = thickness).

KNIT LINE OR LIFT LINE: Interchangeableterms describing the adhesion plane where one passis sprayed over another.

KREBS UNITS (K.U.): A measurement ofviscosity for materials that have the property ofchanging resistance to flow when under shear.Such materials are called thixotropic. Measuring isdone with a Krebs/Stormer viscometer.

L

LAITANCE: A layer of weak non-durablematerial containing cement and fines, brought bybleeding water to the top of overwet concrete.

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Laitance may be detected by scraping the concretesurface with a putty knife; if a quantity of loosepowdery material is observed or easily removed,excessive laitance may be considered to be present.

LATEX: A colloidal dispersion of a polymer orelastomer in water that coalesces into a film uponevaporation of the water. (See EMULSION;COLLOIDAL DISPERSION)

LEADER HEAD: (See CONDUCTOR HEAD)

LIFT: The sprayed polyurethane foam that resultsfrom a pass.

LIVE LOAD: The weight on a roof of temporary,mobile loads such as foot traffic, roofingequipment, water, snow, and ice.

LOW TEMPERATURE FLEXIBILITY: Theability of a membrane or other material to remainflexible (resist cracking when flexed), after it hasbeen cooled to a low temperature.

M

MASTIC: A coating material of relatively thickconsistency.

MATERIAL SAFETY DATA SHEET (MSDS):A standard formatted information sheet prepared bya material manufacturer which describes thepotential hazards, physical properties, andprocedures for safe use of a material.

MECHANICAL BOND: (See BOND,MECHANICAL)

METHYLENE DIPHENYL DIISOCYANATE(MDI): Component A in spray polyurethane foam.An organic chemical compound having two reactiveisocyanate (-N=C=O) groups. It is mixed with theB component to form polyurethane.

MECHANICAL DAMAGE: Breaks or puncturesto insulation and coating systems as a result ofimpact or abrasion.

MEMBRANE: A flexible or semi-flexible roofcovering whose primary function is the exclusion ofwater.

MEMBRANE REINFORCEMENT: Fabrics orfibers embedded in mastic or coating to providestrength and impact resistance.

MIL: One-thousandth of an inch; 0.001 inch(0.025mm). A unit used to measure coatingthickness.

MILDEW: A superficial coating or discoloring ofan organic material due to fungal growth, especiallyunder damp conditions. (See also: MILDEW)

MIST COAT: A very thin sprayed coat.

MOLD: Fungal growths often resulting indeterioration of organic materials, especially underdamp conditions.

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MOISTURE VAPOR TRANSMISSION (MVP):(See WATER VAPOR TRANSMISSION)

MONOLITHIC: Formed from or composed of asingle material; seamless.

MSDS: (See MATERIAL SAFETY DATASHEET)

MUD CRACKING: The defect in an appliedcoating or mastic when it cracks into large segmentsor shrinks (also called alligatoring). When theaction is fine and incomplete, it is usually referredto as “checking.”

MULTIPLE COAT: Two or more layers ofcoating applied to a substrate.

N

NEOPRENE RUBBER: A synthetic rubber havingphysical properties closely resembling those ofnatural rubber. Made by polymerization ofchloroprenes.

NIGHT SEAL: A material and or method used totemporarily seal a membrane edge duringconstruction to protect the roofing assembly inplace from water penetration. May be removedwhen roofing application is resumed.

NON-BREATHING MEMBRANE: A membranematerial that has a significantly greater resistance tothe diffusion of water vapor than the other materialswith which it is used.

NON-FERROUS METAL: All metals that are notiron compounds, i.e., copper, lead, gold, silver, andaluminum. These metals are non-magnetic.

NON-FLAMMABLE: Liquid having nomeasurable FLASH POINT (see also).

NON-OXIDIZING: A material that resistsoxidation in exterior exposures or acceleratedweathering.

NON-VOLATILE CONTENT: That portion of acoating material that does not evaporate undernormal ambient conditions. (For Comparison SeeSOLIDS CONTENT)

NRCA: National Roofing Contractors Association.

O

OFF-RATIO FOAM: Polyurethane which has alack of isocyanate or resin. Off-ratio foam will notexhibit the full physical properties of normal foam.

ORANGE PEEL SURFACE TEXTURE: Thesurface texture of polyurethane foam resemblingthat of an orange peel.

ORGANIC: Compounds containing carbon.

ORIFICE: An opening or aperture. The openingin the tip of a spray gun.

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OVERSPRAY: (1) Airborne spray loss ofpolyurethane foam or coatings. (2) Undesirabledepositions of airborne spray loss.

OVERSPRAY SURFACE TEXTURE: Thesurface shows a linear coarse textured patternand/or a pebbled surface. This surface is generallydownwind of the sprayed polyurethane path and isunacceptable for proper coating coverage andprotection, if severe.

P

PARAPET: A wall or top portion of a wallextending above an attached horizontal surface suchas a roof, terrace, or deck; often used to provide asafety barrier at a roof edge.

PASS: The amount of coating or polyurethanefoam applied by moving the gun from side to sideand moving away from fresh material. A pass isdelineated by its width, length and thickness.

PASS LINES: The overlapping of the polyurethanefoam or coating as the newly applied material tiesinto the previous pass.

PEEL STRENGTH: The average force (or forceper unit width) required to peel a membrane orother material from the substrate to which it hasbeen bonded.

PEELING: Top-coating film inadequately bondedwith undercoats resulting in partial delamination ordetachment of final coat.

PENETRATION: Any object passing through aroof.

PERM: A unit of water vapor transmissiondefined as 1 grain of water vapor per square foot perhour per inch of mercury pressure difference (1 inchof mercury = 0.49 psi).

PERM RATING: The permeance of a material.Breather materials have relatively high permratings, vapor retarders have relatively low permratings, vapor barriers have essentially zero(negligible) perm ratings.

PERMEABILITY: The rate at which water vaporwill diffuse through a unit area of material inducedby a unit differential in water vapor pressure.Permeance values are reported for specificthicknesses (usually recommended applicationthickness). Units are ng/s•m2•Pa (Grains/ft2•hr•inHg.

PERMEANCE: The time rate of water vaportransmission through unit area of water vaportransmission through unit area of flat material orconstruction induced by unit vapor pressuredifference between two specific surfaces, underspecified temperature and humidity conditions.

pH: A measure of acidity/alkalinity of aqueousmixtures. A measure of pH 7 is neutral, lower ismore acidic, higher is more alkaline.

PICTURE FRAMING: Outlining the perimeter ofa stud wall cavity with spray polyurethane foamprior to filling the center.

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PIGMENT: Fine solid particles dispersed in acoating to impart color.

PINHOLE: A small hole in a mastic, coating, orpolyurethane foam.

PLASTICIZER: A substance added to a plasticor coating to increase its flexibility or elongation.

POLYMER: A substance consisting of highmolecular weight chemical compoundscharacterized by chains of repeating simpler units.

POLYOL: Polyol is the main ingredient of theresin component that reacts with the isocyanate toform polyurethane.

POLYURETHANES: A compound based on thereaction of various isocyanates and various polyolresins. These compounds or polymers can createrigid foams, flexible foams, elastomeric coatings orstructural resins and many other forms. They areeither an aromatic or aliphatic polyurethane (Seealso AROMATIC, ALIPHATIC,ISOCYANATE, POLYOL, and RESIN)

POLYURETHANE COATINGS: A one or twopart coating that contains polyisocyanate monomerand a hydroxyl containing resin, which react duringcure to form polyurethane elastomeric.

POPCORN SURFACE TEXTURE: Apolyurethane foam surface texture where valleysform sharp angles. This surface is unacceptable foruniform coating application.

PONDING: The accumulation of water in low-lying areas that exceeds the manufacturer’sspecification and/or contract documents. (SeePOSITIVE DRAINAGE)

POSITIVE DRAINAGE: The condition in whichthere is no consequential standing water on the roof48 hours after a rain. (See PONDING)

POT LIFE: The period of time during which amulti-component or catalyzed material remainssuitable for application after being mixed.

PRIMER: The first layer of coating applied to asurface to improve the adhesion of subsequentlyapplied materials or to inhibit corrosion.

PROPORTIONER: The basic pumping unit forspraying polyurethane foam or two componentcoating systems. Consists of two positivedisplacement pumps designed to dispense twocomponents at a precisely controlled ratio.

PSI: Pounds per square inch.

PSYCHROMETER: A device for measuringambient humidity by employing a dry bulbthermometer and a wet bulb thermometer.

PSYCHROMETRIC CHART: A diagram relatingthe properties of humid air with temperature.

PURGE: To cleanse or remove liquid materialsfrom equipment or hoses.

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Q

QUV: An apparatus used to simulate the effects ofweathering of materials.

R

R VALUE: The resistance of a material to heattransfer. Insulators have relatively high R values.Units are °K•m2/W (°F•ft2•hr/Btu).

RCI: Roof Consultants Institute.

RECOVERING: The process of installing a newroofing system over an existing roofing system.

REGLET: A sheet metal receiver for theattachment of counterflashing. (A reglet may beinset into a raggle, embedded behind cladding, or besurface mounted.)

RELATIVE HUMIDITY: The ratio of absolutehumidity to saturation humidity, expressed as a percent.

REPLACEMENT: The process of removing anexisting roof and installing a new roofing system.

RE-ROOFING: Either recovering or replacementof a roofing system. (See RECOVERING;REPLACEMENT)

RESIN: 1.) Component B in SPF. This componentcontains a polyol catalyst, blowing agent, fire

retardant, and surfactants. It is mixed with the Acomponent to form polyurethane. 2.) General termapplied to a wide variety of more or less transparentand fusible products, which may be natural orsynthetic. Higher molecular weight synthetic resinsare referred to as polymers. 3.) Any polymer that isa basic material for coatings and plastics.

RETROFIT: The modification of an existingbuilding or facility to include new systems orcomponents.

ROOF CURB: Raised frame used to mountmechanical units such as air conditioning or exhaustfans, skylights, etc.

ROOF SLOPE: The angle of a roof surfacemeasured in the number of inches of vertical rise ina horizontal length of 12”.

RUST BLUSH: The earliest stage of rustingcharacterized by an orange or red color. Occursfrequently on freshly sandblasted steel if allowed tostand too long before coating.

S

SADDLE: A relatively small raised substrate orstructure constructed to channel or direct surfacewater to drains or off the roof. A saddle may belocated between drains or in a valley, and is oftenconstructed like a small hip roof or like a pyramidwith a diamond-shaped base. (See CRICKET)

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SAG: Undesirable excessive flow or run inmaterial after application to a sloped or verticalsurface.

SATURATION HUMIDITY: The maximumconcentration of water vapor in air at a giventemperature before condensation occurs.

SBCCI: Southern Building Code CongressInternational. One of the three model buildingcodes.

SCARF: To remove the surface or coating frompolyurethane foam by cutting, grinding, or othermechanical means. Synonymous with SCARIFY.

SCARIFY: (See SCARF)

SCRIM: A woven, non-woven, or knitted fabric,composed of continuous strands of material used forreinforcing or strengthening membranes. Scrimmay be incorporated into a membrane by thelaminating or coating process.

SCUPPER: An opening in a parapet wallallowing runoff water to exit a roof.

SCV: Solid content by volume.

SEALANT: Any of a variety of compounds usedto fill and seal joints or openings in wood, metal,masonry and other construction materials. Somecommon types of sealants are Neoprene®,polysulfide, acrylic latex, butyl, polyurethane,foams and silicone.

SEALANT FOAM: One or two componentpolyurethane foam applied as a bead and used tocontrol air leakage as part of an air barrier systemwithin the building envelope.

SELF-FLASHING: The ability of sprayedpolyurethane foam to be applied around apenetration or at a roof transition without the needfor other materials.

SERVICE TEMPERATURE LIMITS: Themaximum temperature at which a coating,polyurethane foam, or other material will performsatisfactorily.

SET: To convert into a fixed or hardened state bychemical or physical action.

SHELF LIFE: The period of time within which amaterial remains suitable for use. Synonymous withSTORAGE LIFE.

SHORE HARDNESS: A measure of hardnessbased on the shore scale.

SILICONE COATING: A liquid appliedelastomeric coating whose principal polymer in thedispersion contains more than 95% silicone resin.

SKINNING: The formation of a dense film on thesurface of a liquid coating or mastic.

SLIT SAMPLES: Small cut samplesapproximately 2” long, ½” wide, and ¾” deepwhich are taken for evaluation of sprayed materials.

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SMOOTH SURFACE TEXTURE: The surfaceshows spray undulation and is ideal for receiving aprotective coating.

SOLIDS CONTENT: The percentage ofnon-volatile matter in a coating or masticformulation; may be expressed as a volume orweight percent.

SOLVENT: A liquid that dissolves othersubstances. (See also: THINNER)

SPI: The Society of the Plastics Industry.

SPI / SPFD: The Society of the Plastics Industry /Spray Polyurethane Foam Division.

SPRAY POLYURETHANE FOAM (SPF): Afoamed plastic material, formed by spraying twocomponents, isocyanate (A component) and a resin,(B component) to form a rigid, fully adhered, water-resistant, and insulating membrane.

SPUD: To remove the roofing aggregate and mostof the bituminous top coating by scraping andchipping.

SQUARE: A standard measurement for roofingarea equal to 100 square feet. Also called “roofingsquare.”

STORAGE LIFE: (See SHELF LIFE)

STRESS: An applied force which tends to deforma body. May be tensile stress (pulling or stretching

force), compressive stress (pushing or compactingforce) or shear stress (opposite but offset parallelforces tending to produce a sliding motion).

STRESS-CRACK: External or internal crackswithin a material caused by long term stress.

SUBSTRATE: The surface to which polyurethanefoam is applied.

SURFACE EROSION: The wearing away of asurface due to abrasion, dissolution, or weathering.

SURFACE TEXTURE: The resulting surfacefrom the final pass of SPF. The following terms areused to describe the types of SPF surfaces: smooth,orange peel, coarse orange peel, verge of popcorn,popcorn, treebark, and overspray.

SURFACING: The top layers of a roof covering,specified or designed to protect the underlyingroofing from direct exposure to the weather.

SURFACTANT: Short for “surface active agent.”Used to alter the surface tension of liquids. Aningredient in polyurethane foam formulations to aidin mixing and controlling cell size.

T

TACK-FREE: A curing phase of polyurethanefoam wherein the material is no longer sticky.

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TEAR STRENGTH: The maximum force requiredto tear a specimen, the force acting substantiallyparallel to the major axis of the test specimen.Values reported as a stress per unit of thickness.

TENSILE STRENGTH: The tensile (pulling orstretching) force necessary to rupture a materialsample divided by the sample’s original crosssectional area. Units are usually kPa or psi or lb/in2.

TERMINATION: The treatment or method ofanchoring and/or sealing the free edges of themembrane in roofing or waterproofing system.

THERMAL BARRIER: A material applied overpolyurethane foam designed to slow the temperaturerise of the foam during a fire situation and delay itsinvolvement in the fire. Thermal barriers for usewith polyurethane foam must have a time rating ofnot less than 15 minutes.

THERMAL BRIDGE: A thermally conductivematerial which penetrates or bypasses an insulationsystem; such as a metal fastener or stud.

THERMAL CONDUCTANCE (C): A unit ofheat flow that is used for a specific thickness ofmaterial or for materials of composite construction,such as laminated insulation. C=k/thickness. Unitsare W/m2•°K or Btu/hr•ft2•°F.

THERMAL CONDUCTIVITY (k): The heatenergy that will be transmitted by conductionthrough 1 square foot of 1 inch thick homogeneousmaterial in one hour when there is a difference of 1degree Fahrenheit perpendicularly across the two

surfaces of the material. Units are W/m•°K orBtu•in/hr•ft2•°F.

THERMAL MOVEMENT: Changes in dimensionof a material as a result of temperature changes.

THERMAL RESISTANCE (R): An index of amaterial’s resistance to heat flow; it is the reciprocalof thermal conductance (C) or the thickness dividedby k.

THERMAL SHOCK: The stress producingphenomenon resulting from sudden temperaturedrops in a roof membrane, for example, a rainshower following brilliant sunshine.

THERMOGRAPHY: A technique used to locatewet areas in a roof assembly by measuringdifferences in temperature.

THERMOPLASTIC: A polymeric materialwhich softens upon heating and hardens uponcooling.

THERMOSET: A polymeric material whosephysical properties are relatively unaffected bymodest changes in temperature; when heated,thermosets will degrade rather than melt.

THINNER: A liquid used to reduce the viscosityof coatings or mastics. Thinners evaporate duringthe curing process. Thinners may be used assolvents for clean up of equipment.

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THIXOTROPIC: Having the property ofdecreasing viscosity with increasing shear stress. Acoating is thixotropic if it thins with stirring orpumping but thickens back up when movementceases.

TIE IN LINES: The starting or stopping point atwhich new foam is applied to foam which had beensprayed earlier.

TINT: A color produced by the introduction ofsmall amounts of a colored pigment.

TOXICITY: The quality, property, or degree ofbeing poisonous or toxic.

TREEBARK SURFACE TEXTURE: A rollingfoam surface texture where the valleys form sharpangles generally caused by spraying foam at anangle. This surface is unacceptable for coatingapplication.

TWIST & RACK: Colloquial name for ASTMStandard E72, “ Standard Methods of ConductingStrength Tests of Panels for Building Construction.”ASTM E72 tests a stud wall’s resistance to wind,seismic, and weight loads.

TWO-PART SYSTEM: A coating or polyurethanefoam formed by the mixing and the reaction of twodifferent materials.

U

UBC: Uniform Building Code. Model buildingcode generated by ICBO.

UL: Underwriter’s Laboratory. An independenttesting agency.

ULTRA-VIOLET RADIATION (UV):Electro-magnetic radiation beyond the visiblespectrum at its violet end. Invisible high-energysunlight which degrades many organic materials.

UNDERLAYMENT: A material that is laid downas a substrate for the sprayed polyurethane foam tomake the surface smooth or to give a specific ratingfor interior fire exposures.UPLIFT: (See WIND UPLIFT)

UV: An abbreviation for ultraviolet. (See also:ULTRAVIOLET RADIATION)

U VALUE: Overall thermal conductance. U valueis equal to the inverse of the sum of the R-values ina system (U = 1/R total). Units are °K•m2/W(°F•ft2•hr/Btu).

V

VAPOR BARRIER: A material that prevents themigration of water vapor across it.

VAPOR MIGRATION: The movement of watervapor from a region of high vapor pressure to aregion of lower vapor pressure.

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VAPOR PRESSURE: The portion of atmosphericpressure contributed by water vapor; an indicator ofabsolute humidity. Units are kPa (in Hg).

VAPOR RETARDER: A film, coating, sheet, orother building component which restricts themigration of water vapor relative to the buildingcomponents with which it is used.

VERGE OF POPCORN SURFACE TEXTURE:The roughest texture suitable for receiving theprotective coating on a sprayed polyurethane foamroof. The surface shows a texture where nodulesare larger than valleys, with the valleys relativelycurved. This surface is acceptable for receiving aprotective coating only because of the relativelycurved valleys. However, the surface is consideredundesirable because of the additional amount ofcoating material required to protect the surfaceproperly.

VISCOSITY: The thickness or resistance to flowof a liquid. Viscosity generally decreases astemperature increases.

VOC: Abbreviation for Volatile OrganicCompounds. (See VOLATILE ORGANICCOMPOUNDS)

VOLATILE ORGANIC COMPOUNDS: Anycompound containing carbon and hydrogen orcontaining carbon and hydrogen in combinationwith other elements that has a vapor pressure of 1.5pounds per square inch absolute (77.6 mm Hg) orgreater under actual storage conditions.

W

WALKWAYS: High traffic and high serviceareas on a rooftop, particularly those with vents,hatches, and heavy duty air conditioning units, thathave been reinforced with extra coating andgranules to prevent damage to the polyurethanefoam system.

WATER ABSORPTION: The percent increase inweight of a specimen after contact with water for aspecified time.

WATER VAPOR TRANSMISSION: Themigration of water vapor.

WATER VAPOR TRANSMISSION RATE: Therate at which water vapor will diffuse through a unitarea of material. Units are usually grains/ft2•hr.

WET BULB TEMPERATURE: The temperatureof air as registered by a thermometer whose bulb iscovered by a water wetted wick. Units are °C or °F.

WET FILM GAUGE: A gauge for measuring thethickness of wet coating as applied to a flat smoothsurface.

WET FILM THICKNESS: The thickness,expressed in mm or MILS, of a coating or mastic asapplied but not cured. (For comparison, See DRYFILM THICKNESS) (See MILS)

WINDSCREEN: A device to minimize the effectsof wind on coating or polyurethane foamapplication.

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WIND UPLIFT: The force caused by thedeflection of wind at roof edges, roof peaks, or

obstructions causing a drop in air pressureimmediately above the roof surface.

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