Accelerated Weathering: machine-made tests in which coatings or roofing materials are exposed to a controlled environment where various exposures such as heat, water, condensation, or light are altered to magnify their effects, thereby accelerating the weathering process.

Acid Rain: rain with pH values < about 7; commonly results from acids formed by pollutants.

Acrylic Latex: aqueous dispersion, thermoplastic or thermosetting, of polymers or copolymers of acrylic acid, methacrylic acid, esters of these acids, or acrylonitrile.

Acrylics: resins resulting from the polymerization of derivatives of acrylic acids, including esters of acrylic acid, methacrylic acid, acrylonitrile, and their copolymers.

Additive: any substance added in small quantities to paints or coatings usually to improve properties.

Adhere: to cause two surfaces to be held together by adhesion.

Adhesion Promoters: materials built into the binder or added to the paint to form primary bonds to either the substrate or the previously applied coating with the specific aim of improving the dry or wet adhesion, or both.

Aggregate: rock, stone, crushed stone, crushed slag, water-worn gravel or marble chips used for surfacing and/or ballasting a roof system

Airless Spraying: process of atomization of a paint or coating by forcing it through an orifice at high pressure.

Alligatoring: a type of crazing or surface cracking of a definite pattern, as indicated by its name. The effect is often caused during weather aging. On built-up roofs the cracks may or may not extend through the surfacing bitumen.

Application Rate: the quantity (mass, volume, or thickness) of material applied per unit area.

Aqueous: water-containing or water-based.

Architectural Coatings: organic coatings intended for on-site application at ambient temperatures to interior or exterior surfaces of residential, commercial, institutional, industrial, or government structures.

Asbestos: a group of natural, fibrous silicate materials used to reinforce some roofing materials and common in transite roof panels.

Asphalt: a dark brown or black substance found in a natural state or, more commonly, left as a residue after evaporating or otherwise processing crude oil or petroleum; asphalt may be further refined to conform to various roofing grade specifications.

Asphalt Emulsion: a suspension or emulsion of ordinary asphalt in water.

Asphalt Roof Cement: a trowelable mixture of solvent-based bitumen, mineral stabilizers, other fibers and/or fillers.

Ballast: an anchoring material, such as aggregate, or precast pavers, which employ the force of gravity to hold (or assist in holding) single-ply roof membranes in place.

Barrier Coat: coating used to isolate a paint system from the surface to which it is applied in order to prevent chemical or physical interaction between them, e.g., to prevent the paint solvent attacking the underlying paint or to prevent bleeding from underlying paint or material.

Basecoat: the first coat applied to a surface, as paint; a prime coat.

Base Ply: the lowermost ply of roofing in a roof membrane or roof system.

Base Sheet: an impregnated, saturated, or coated felt placed as the first ply in some multi-ply built-up and modified bitumen roof membranes.

Bleeding: the diffusion of colorants through a coating from a previously painted substrate due to the action of the vehicle or solvent or both. The action is dependent on the pigments, vehicles, and solvents of the systems.

Blister: undesirable elevation of a coating; an enclosed pocket of air, which may be mixed with water or solvent vapor, trapped between impermeable layers of felt or membrane, or between the membrane and substrate.rounded

Blistering: formation of dome-shaped hollow projections in paints or coating films resulting from local loss of adhesion and lifting of the film from the underlying surface.

BOCA: Building Officials and Code Administrators, International, Inc. (author of the BOCA National Building Code).

Bond: coatings – adhesion between a coating and substrate to which it has been applied.

Bridging: when the roof membrane is unsupported at a juncture.

Broadcast: to apply or sprinkle solid particles on an uncured coating surface.

British Thermal Unit (BTU): the heat energy required to raise the temperature of one pound of water one degree Fahrenheit (joule).

Brooming: an action carried out to facilitate embedment of a ply of roofing material into hot bitumen by using a broom, squeegee, or special implement to smooth out the ply and ensure contact with the bitumen or adhesive under the ply; using the same process to embed and smooth out a ply of polyester roofing reinforcement into an elastomeric coating

Built-up Roofing (BUR): a continuous, semiflexible membrane consisting of plies of saturated felts, coated felts, fabrics, or mats assembled in place with alternate layers of bitumen, and surfaced with mineral aggegate, bituminous materials, or a granule surfaced sheet.

Cant Strip: a beveled or triangular shaped strip of wood, wood fiber, perlite, or other material designed to serve as a gradual transitional plane between the horizontal surface of a roof deck or rigid insulation and a vertical surface

Cap Sheet: granule-surface coated sheet used as the top ply of some built-up or modified bitumen roof membranes and/or flashing.

Capacitance Meter: a device used to locate moisture or wet materials within a roof system by measuring the ratio of the change to the potential difference between two conducting elements separated by a non-conductor.

Caulking Compound: soft, plastic, putty-like material, consisting of pigment and vehicle, used for sealing joints in buildings and other structures where normal structural movement may occur, or for preventing leakage.

Caulking: the physical process of sealing a joint or juncture; sealing and making weather-tight the joints, seams, or voids between adjacent units by filling with a sealant.

Chalking: formation of a friable powder (pigment rich) on the surface of a paint film caused by the disintegration of the binding medium due to disruptive factors during weathering. The chalking of a paint film can be considerably affected by the choice and concentration of the pigment. (BSI) It can also be affected by the choice of the binding medium.

Chlorinated Polyethylene (CPE): a thermoplastic material, used for single-ply roof membranes, composed of high molecular weight polyethylene which has been chlorinated—a process that yields a flexible rubber-like material.

Chlorosulfonated Polyethylene (CSPE): (probably best known by the DuPont trade name HypalonTM) a synthetic, rubber-like thermoset material, based on high molecular weight polyethylene with suphonyl chloride, formulated to produce a self-vulcanizing roof membrane.

Closure Strip: a metal or resilient strip, such as neoprene foam, used to close openings created by joining metal panels or sheets and flashings.

Coalescence: the formation of a film of resinous or polymeric material when water evaporates from an emulsion or latex system, permitting contact and fusion of adjacent latex particles; action of the joining of particles into a film as the volatile evaporates.

Coal Tar: a dark brown to black colored, semi-solid hydrocarbon obtained as residue from the partial evaporation or distillation of coal tars. Coal tar pitch is further refined to conform to roofing grade specifications.

Coat: paint, varnish, or lacquer applied to a surface in a single application (one layer) to form a properly distributed film when dry.

Coating: generic term for paints, lacquers, enamels, printing inks, etc.

Cohesion: the degree of internal bonding of one substance to itself.

Color: one aspect of appearance; a stimulus based on visual response to light, and consisting of the three dimensions of hue, saturation, and lightness.

Cold Process Built-Up Roof: a continuous, semi-flexible roof membrane, consisting of a ply or plies of felts, mats or other reinforcement fabrics that are laminated together with alternate layers of liquid-applied (usually asphalt-solvent based) roof cements or adhesives installed at ambient or a slightly elevated temperature.

Composite: homogeneous material created by the synthetic assembly of two or more materials.

Concrete: a composite material which consists essentially of a binding medium within which are embedded particles or fragments or aggregate; in Portland cement concrete, the binder is a mixture of Portland cement and water.

Contact Cements: adhesives used to adhere or bond various roofing components; these adhesives adhere mated components immediately on contact of surfaces to which the adhesive has been applied.

Coping: the covering piece on top of a wall which is exposed to the weather, usually made of metal, masonry, or stone. It is preferably sloped to shed water back onto the roof.

Cornice: the decorative horizontal molding or projected roof overhang.

Corrosion: the deterioration of metal or of concrete by chemical or electrochemical reaction resulting from exposure to weathering, moisture, chemicals, or other agents in the environment in which it is placed.

Corrosion Inhibitor: any of a number of materials used to prevent the oxidation of metals; may be a coating applied to the surface, a paint undercoat, an additive, or an element alloyed with the metal.

Counterflashing: formed metal sheeting secured on or into a wall, curb, pipe, rooftop unit, or other surface, to cover and protect the upper edge of the membrane base flashing or underlying metal flashing and associated fasteners from exposure to the weather.

Coverage: spreading rate generally expressed in ft/gal or meres/litre. In pigmented coatings, it is related to hiding power. In clear coatings, it refers to the area coated at a desired film thickness.

Cracking: generally, the splitting of a dry paint or coating film, usually as a result of aging.

Cricket: an elevated roof substrate or structure, constructed to divert water around a chimney, curb, away from a wall, expansion joint, or other projection/penetration.

Cross Coating: application of a coat of paint by a series of strokes or spray passes, each at right angles to the previous series.

Crosslinking: applied to polymer molecules, the setting up of chemical links between the molecular chains to form a three-dimensional or network polymer generally by covalent bonding.

Cupola: a relatively small roofed structure, generally set on the ridge or peak of a main roof area.

Curb: a raised member used to support roof penetrations, such as skylights, mechanical equipment, hatches, etc. above the level of the roof surface; a raised roof perimeter relatively low in height.

Cure Time: the period of time that a reacting thermosetting plastic is exposed to specific conditions to reach a specified property level.

Curing: the toughening or hardening of a coating film as a result of elevated temperature or significant reaction other than simple oxidation.

Dead Level: essentially horizontal or flat, as in a roof deck or rooftop with no intentional slope to the roof drains. Also referred to as zero (0) slope.

Deck: a structural component of the roof of a building. The deck must be capable of safely supporting the design dead and live loads, including the weight of the roof systems, and the additional live loads required by the governing building codes. Decks are either non-combustible (e.g., corrugated metal, concrete, or gypsum) or combustible (e.g., wood plank or plywood), and provide the substrate to which the roofing or waterproofing system is applied.

Deck Paint: a paint having a high degree of resistance to mechanical wear; esp. used on surfaces such as porch floors and ships’ decks

Degradation: change in characteristics or quality of the original substance through chemical breakdown or physical wear.

Delaminate: to separate existing layers.

Dew Point: that temperature at which water pressure present in the atmosphere is just sufficient to saturate it.

Diffusion: the movement of water vapor from regions of high concentration (high water vapor pressure) toward regions of lower concentration (due to random thermal molecular motion).

Dimensional Stability: the ability of a material to resist change in length, width, and/or thickness that results from exposure to elevated or freezing temperatures, and moisture, over time.

Discoloration: staining; also changing or darkening in color from the standard or original.

Dispersion: process of dispersing a dry powder (or pigment) in a liquid medium in such a way that the individual particles of the powder become separated from one another and are reasonably evenly distributed throughout the entire liquid medium.

Drip Edge: a metal flashing, or other overhanging component, with an outward projecting lower edge, intended to control the direction of dripping water and help protect underlying building components. A drip edge also can be used to break the continuity of contact between the roof perimeter and wall components to help prevent capillary action.

Dry: a paint film is considered dry when it feels firm to the finger, using moderate pressure.

Drying Time: time required for an applied film of a paint or coating to reach the desired stage of sure, hardness, or nontackiness.

Durability: the degree to which paints or coatings can withstand the destructive effect of the conditions to which they are subjected and how long they retain an acceptable appearance and continue to protect the substrate.

Durometer: instrument for measuring the surface hardness of rubber, plastic, or protective coatings.

Efflorescense: (for exterior paints) an incrustation of soluble salts, commonly white, deposited on the surface of coatings, stone, brick, plaster, or mortar; usually caused by salts or free alkalies leached from mortar or adjacent concrete as moisture moves through it.

Elastic: ability of a substance to return to its approximate original shape or volume after distorting force on the substance has been removed.

Elastic Limit: maximum stress a material can withstand and still return to its original size and shape after the force is removed.

Elasticity: property by which a material tends to recover its original size and shape immediately after removal of the force causing deformation.

Elastomer: a natural or synthetic polymer which, at room temperature, can by stretched repeatedly to at least twice its original length and which after removal of the tensile load will immediately and forcibly return to approximately its original length.

Elastomeric: rubberlike; relating to or having the properties of elastomers.

Elastomeric Coating: a coating system which, when fully cured, is capable of being stretched at least twice its original length (100% elongation) and recovering to its original dimensions.

Elongation: the increase in specimen length form the point of initial load application to the point of film rupture in a tension test.

Embedment: the process of installing or pressing-in a reinforcement felt, fabric, mat or panel uniformly into bitumen, coating or adhesive

Energy Star: ENERGY STAR is a joint program of the U.S. Environmental Protection Agency and the U.S. Department of Energy developed to help save money and protect the environment through energy efficient products and practices.

Environmentally preferable: products or services that have a lesser or reduced effect on the environment.

Erosion: wearing away of the top coating of a painted surface, e.g., by chalking, or by the abrasive action of windborne particles of grit, which may result in exposure of the underlying surface.

Erosion Resistance: the ability of a paint or coating to withstand being gradually worn away by chalking or by the abrasive action of water or windborne particles of grit.

Etch: wear away or roughen a surface with, or as if with, an acid. Erode is sometimes used as a synonym.

Expansion Joint: a structural separation between two building elements that allows free movement between the elements without damage to the roofing or waterproofing system.

External Plasticizer: post added plasticizer as opposed to plasticization by means of internally combined groups, such as copolymerization.

Exudation: the migration of a substance to the surface, such as resin form wood, plasticizer form films.

Feathering: operation of tapering off the edges of a coat of paint by laying off with a comparatively dry brush or roller.

Field of the Roof: the central or main portion of a roof, excluding the perimeter and flashing.

Film: a layer of one or more coats of paint covering an object or surface.

Film Thickness: thickness of any applied paint or coating, wet or dry.

Fineness of Grind: a numerical assessment of the degree of dispersion or of the presence of coarse particles in pigmented coatings as determined by the protrusion of particles or agglomerates through the wet film at a given thickness.

Fire Resistance: the property of a material or assembly to withstand fire or give protection from it.

Fire Retardant
: implies that the described product, under accepted methods of test, will significantly: (a) reduce the rate of flame spread on the surface of a material to which it has been applied; (b) resist ignition when exposed to high temperatures; or (c) insulate a substrate to which it has been applied and prolong the time required to reach its ignition, melting, or structural-weakening temperature.

Fishmouth: a half-cylindrical or half-conical shaped opening or void in a lapped edge or seam, usually caused by wrinkling or shifting of ply sheets during installation

Flash Rusting: is a form of corrosion that occurs during the drying process of a water-based paint or coating. Water-soluble corrosion products migrate to the surface of a coating and appear as a stain.

Flashing: components used to weatherproof or seal the roof system edges at perimeters, penetrations, walls, expansion joints, valley, drains, and other places where the roof covering is interrupted or terminated. For example, membrane base flashing covers the edge of the field membrane, and cap flashings or counterflashings shield the upper edges of the base flashing.

Flat Paint: paint which dries to a surface which scatters the light falling on it, so as to be substantially free form gloss or sheen.

Flex Cracking: development of small cracks in flexible articles or coatings when these articles are subjected to repeated flexing or bending.

Flexibility: degree to which a coating after drying is able to conform to movement or deformation of its supporting surface, without cracking or flaking.

Glass Transition: the transition temperature range (relatively small for most polymers) within which an amorphous polymer changes from a rubbery or viscous to glass-like (brittle) state.

Gloss: subjective term used to describe the relative amount and nature of mirrorlike (specular) reflection. Different types of gloss are arbitrarily differentiated, such as sheen, distinctness-of-image gloss, etc.

Gloss Retention: degree to which the original sheen of a coating is retained.

Green Roof: roof planted with a full or partial covering of vegetation.

Hairline Cracks: very fine cracks which do not penetrate the topcoat; they occur erratically and at random.

Hardness: ability of a coating film, as distinct from its substrate, to resist cutting, indentation, or penetration by a hard object.

Hiding Power: the ability of a paint or coating to hide or obscure a surface over which it has been applied uniformly.

High Build: producing think, dry films per coat.

High-Solids Coatings: coatings containing about 70% or more solids by weight.

Holiday Detector: device for detection of pinholes or voids in coating film.

Humidity: the condition of the atmosphere in respect to water vapor.

Hydroblasting: cleaning with high-pressure water jet.

Hydrophilic: substance which absorbs or exhibits affinity for water; wettable.

Hydrophobic: substance with does not absorb or exhibit affinity for water, nonwettable.

Impact Resistance: ability of a coating to resist a sudden blow.

In-Can Preservative: biocide used to prevent bacterial growth in the paint that can cause odor or produce enzymes that can break down cellulosic thickeners.

Industrial Maintenance Coatings: coatings which are applied to factory-made articles (before or after fabrication) usually with the help of special techniques for applying and drying – in contrast to architectural paints.

Insulate: to prevent the passage of heat, electricity, or sound into or out of, especially by surrounding with a nonconducting material.

Intercoat Adhesion: the ability of a paint or coating to adhere to previously applied films.

Internal Plasticizer: where the plasticizing agent is chemically combined with the hard resin or polymer, the product is said to be internally plasticized.

Internally Plasticized: when a product is synthesized from a reaction involving two or more raw materials, it may be said to be internally plasticized if one of the raw materials is able to confer plasticity or flexibility to it. In other words, the product is plasticized because it is built up from a component which is naturally plastic.

Intumescence: the puffing up of a coating on contact with high heat (fire) which results in a foamlike structure that insulates the substrate.

Intumescent Coating: fire-retardant coating which, when heated, becomes plastic and produces nonflammable gases, such as carbon dioxide and ammonia.

Iron Oxides: Fe2O3. Pigments which are substantially oxides of iron.

Krebs-Stormer Viscosimeter: this is the most commonly used viscometer in the paint industry. Paint consistency is measured by its resistance to stirring by a two-vane paddle.

Lap: region where a coat extends over an adjacent fresh coat. The object of the painter is usually to effect a joint between the two coats without showing the lap; to place one coat of finishing material alongside another, partly extending over it, causing increased thickness where the two coats are present.

Latex: stable dispersion of a polymeric substance in an essentially aqueous medium

Latex Paint: a paint containing a stable aqueous dispersion of synthetic resin, produced by emulsion polymerization, as the principal constituent of the binder.

Leafing: the action of particles of certain metallic and other pigments, in the form of thin flat flakes in aligning themselves with or floating on or near the surface of the vehicle.

Letdown: the process of paint manufacturing in which the pigment paste (mill base) is reduced (letdown) by the addition of the remaining ingredients of the formula.

Leveling: the measure of the ability of a wet paint or coating to flow out to a smooth dry film after application so as to obliterate any surface irregularities such as brush marks, roller marks, orange peel from spraying, peaks, or craters which have been produced by the mechanical process of applying the film.

Life Cycle Assessment: analyzing a product’s entire life from raw materials through manufacture, use, and disposal.

Life Cycling Costing: a method of economic analysis that takes into account expected costs over the useful life of an asset.

Lightfastness: the relative degree of change or lack of change in color of paint or coating exposed to the same amount and character of light. Thus, lightfastness is a relative term dependent on conditions which must be defined.

Maintenance Paints: coatings used to maintain bridges, manufacturing plants, offices, stores, and other commercial structures, hospitals and nursing homes, schools and universities, government and public buildings, and both building and nonbuilding requirements in such areas as public utilities, railroads, roads, and highways, and including industrial paint, other than the original coatings, the primary function of which is protection.

Mandrel Bend Test: test for determining the flexibility and adhesion of surface coatings, so named because it involves the bending of coated metal panels around mandrels.

Masonry Paint: an alkali-resistant coating, usually a latex paint, used for masonry substrates.

Mastic: adhesive composition. Loosely used to describe a plastic filler, stopper, putty, or adhesive. Not to be confused with gum mastic, which is a natural resin used for picture varnish.

Material Safety Data Sheets: OSHA’s established guidelines for the descriptive data that should be concisely provided on a data sheet to serve as the basis for written hazard-communication programs. The thrust of the law is to have those who make, distribute, and use hazardous materials be responsible for effective communication.

Mechanical Properties: those properties of a material that are associated with elastic and inelastic reaction when force is applied, or that involve the relationship between stress and strain.

Membrane: a flexible or semiflexible roof covering or waterproofing, whose primary function is the exclusion of water.

Metal Primer: the first coat of paint on metal; a primer, one coat.

Mil: a unit of measure, one mil is equal to 0.001 inches or 25.400 microns, often used to indicate the thickness of a roofing membrane.

Mildew Resistance: the ability of a paint or coating to resist superficial fungus growth that can cause discoloration and ultimate decomposition of a coating’s binding medium.

Mildewcide: chemical agent which destroys, retards, or prevents the growth of mildew

Mineral-Surfaced Roofing: roofing materials whose surface or top layer consists of mineral granules.

Moisture Vapor Transmission: rate of movement of moisture vapor through a membrane.

Mudcracking: paint film defect characterized by an irregular broken network of cracks in the film.

Nap: the dense, soft, or fuzzy fabric attached to a cylindrical cover used on paint rollers.

Neoprene: a synthetic rubber (polychloroprene) used in liquid-applied and sheet-applied elastomeric roof membranes or flashings.

Opaque: impervious to light rays.

Open Time: length of time a coating remains wet enough to allow for brushing-in at the laps.

Paint: verb: to apply a think layer of a coating to a substrate by brush, spray, roller, immersion, or any other suitable means; noun: any pigmented liquid, liquefiable, or mastic composition designed for application to a substrate as a think layer which is converted to an opaque solid film after application. Used for protection, decoration, or identification, or to serve some functional purpose such as the filling or concealing of surface irregularities, the modification of light and heat radiation characteristics, etc.

Parapet Wall: that part of a perimeter wall immediately adjacent to the roof which extends above the roof.

Pearlescent Pigment: used to obtain pearly luster, iridescent effects, and metallic sheen. The pigment particles are transparent, thin platelets of high refractive index which partially reflect and partially transmit incident light; simultaneous reflection from many layers of oriented platelets creates a sense of depth that is characteristic of nacreous luster.

Perm: a unit of measurement of water vapor permeance

Permeability: see water vapor permeance.

Phased Application: the installation of separate roof system or waterproofing system component(s) during two or more separate time intervals.

Pigment: finely ground, natural or synthetic, inorganic or organic, insoluble dispersed particles (powder) which, when dispersed in a liquid vehicle to make paint, may provide, in addition to color, many of the essential properties of a paint – opacity, hardness, durability, and corrosion, resistance.

Pinholes: film defect characterized by small porelike flaws in a coating which extend entirely through the applied film and have general appearance of pin pricks, fine holes, or voids when viewed by reflected light.

Plasticizer: an additive in a paint formulation to soften the film, thus giving it better flexibility, chip resistance, and formability.

Plasticizer Migration: movement of plasticizer in a coating or plastic to the surface or into an adjacent material such as an undercoat or substrate.

Ponding: the excessive accumulation of water at low-lying areas on a roof.

Positive Drainage: the drainage condition in which consideration has been made during design for all loading deflections of the deck, and additional roof slope has been provided to ensure drainage of the roof area within 48 hours of rainfall, during ambient drying conditions.

Primer: first complete coat of paint of a painting system applied to an uncoated surface prior to application of an intermediate coat or topcoat.

Protective Coatings: a think layer of metal, or organic material, as a paint applied to a surface, primarily to protect it from oxidation, weathering, and corrosion.

Quality Control: the maintenance and statement of the quality of a product (data set, etc.) specifically that it meets or exceeds some minimum standard based on known, testable criteria.

QUV: an accelerated weathering machine that simulates the deterioration, caused by water as rain and dew and ultraviolet light energy in sunlight, of outdoor materials.

Re-Cover: the addition of a new roof membrane or steep-slope roof covering over a major portion of an existing roof assembly. This process does not involve removal of the existing roofing.

Reduce: to add a solvent or thinner to a paint or coating for the purpose of lowering its viscosity and/or nonvolatile content.

Rehabilitate: To repair a structure and make it usable again while preserving those portions or features of the property that are historically and culturally significant. For example, rehabilitation might include an updated kitchen while retaining the historic stairwell and fireplaces.

Renovate: to repair a structure and make it usable again, without attempting to restore its historic appearance or duplicate original construction methods or material.

Reroofing: the process of re-covering, or tearing-off and replacing an existing roof system.

Ridge Cap: a material or covering applied over the ridge of a roof.

Roll Roofing: smooth-surfaced or mineral-surfaced, coated, prepared felts.

Roof Assembly: an assembly of interacting roof components (includes the roof deck, vapor retarder [if present],insulation, and roof covering).

Roof System: a system of interacting roof components, generally consisting of membrane or primary roof covering and insulation (not including the roof deck) designed to weatherproof and, sometimes, to improve the building’s thermal resistance.

Rust: the reddish, brittle coating formed on iron or its alloys resulting from exposure to humid atmosphere or chemical attack.

Rust Resistance: the ability of a coating to protect the substrate of iron or its alloys from rusting.

Sealant: a mixture of polymers, fillers, and pigments used to fill and seal joints where moderate movement is expected; unlike caulking, it cures to a resilient solid.

Sealer: (1) a liquid coat which seals wood, plaster, etc., and prevents the surface form absorbing paint ; may be transparent; may act as a primer for a following coat or as a finish for the surface; (2) a coat, applied in liquid form, which is laid over a tar-like substance to prevent its bleeding through an applied paint film.

Shelf Life: the period of time in which a material may normally be stored and still be in a usable condition.

Single-Ply Membranes: roofing membranes that are field applied using just one layer of membrane material (either homogeneous or composite) rather than multiple layers.

Single-Ply Roofing: a roofing system in which the principal roof covering is a single layer flexible membrane, often of thermoset, thermoplastic, or polymer modified bituminous compounds.

Smooth Surfaced Roof: a roof membrane without mineral granule or aggregate surfacing.

Solids by Volume: the volume of the nonvolatile portion of a composition divided by the total volume, expressed as a percent.

Spreading Rate: the average area covered by a specified volume of a paint or coating when applied over normal surface in a manner appropriate for that coating.

Square: 100 square feet of roof area.

Stucco: an exterior finish, usually textured; composed of Portland Cement, lime, and sand, which are mixed with water.

Substrate: any surface to which a paint or coating is applied.

Surface Conditioner: preparatory coating applied to a chalked surface to bind chalk to the substrate, prior to topcoating.

Surface Drying: the premature drying of the surface of a liquid coating film, so that the under portion is retarded in drying.

Surface Preparation: any mechanical or chemical method used to make a substrate more receptive to good adhesion and uniform appearance of the coating to be applied.

Surfactants: contracted from surface active agents, these are additives which reduce surface tension and may form micelles and thereby improve wetting (wetting agents); help disperse pigments (dispersants); inhibit foam (defoamers); or emulsify (emulsifiers).

Tacky: the stage in the drying of a paint at which the film appears sticky when lightly touched with the finger.

Thermal Movement: changes in dimension of a material as a result of temperature changes.

Thermal Shock: the stress-producing phenomenon resulting from sudden temperature changes in a roof membrane when, for example, a cold rain shower follows brilliant hot sunshine, which may result in sudden cooling or rapid contraction of the membrane.

Thermal Stress: stress introduced by uniform or non-uniform temperature change in a structure or material that is contained against expansion or contraction.

Thermoplastic: capable of being repeatedly softened by heat and hardened by cooling.

Thermoset: a material which will undergo or has undergone a chemical reaction by the action of heat, catalysts, ultraviolet light, etc., leading to a relatively infusible state.

Thixotropic Paint: paint which, while free-flowing and easy to manipulate under a brush, sets to a gel within a short time when it is allowed to remain at rest.

Tinting: final adjustment of the color of a paint to the exact color required.

Titanium Dioxide: a high-opacity, bright white pigment, nonchalking type, used as a prime pigment in paints, rubber, plastics.

Topcoat: the coating intended to be the last coat applied in a coating system; usually applied over a primer, undercoaters, or surfacers.

Urban Heat Islands: a metropolitan area which is significantly warmer than its surrounding rural areas. Dark-colored surfaces absorb heat from the sun more than light-colored surfaces. In urban areas, a combination of dark surfaces and a lack of shade intensify this effect.

Vapor Barrier: a moisture-impervious layer or coating (such as special paint, or a membrane on roofing felt or on building paper) which prevents the passage of moisture or vapor into a material or structure.

Viscosity: the property of a fluid whereby it tends to resist relative motion within itself. If different layers of fluid are moving with different velocities, viscous forces come into play, tending to slow down the faster-moving layers and to increase the velocity of the slower-moving layers.

Viscous: having relatively great viscosity.

VOC: abbreviation for volatile organic compound.

Volatile: the easily evaporated components of any coating composition in contrast to the nonvolatile components.

Volatile Content: the quantity, expressed as a weight percent of the powder coating, which is lost under specified conditions of temperature and time.

Waterblasting: blast cleaning of metal using high velocity water.

Waterproof: the quality of a membrane, membrane material, or other component to prevent water entry.

Waterproofing: treatment of a surface or structure to prevent the passage of water under hydrostatic pressure.

Water Repellant System: an exterior coating system for above grade concrete or masonry which temporarily repels water but which is not intended to prevent the passage of moisture under hydrostatic pressure.

Water Resistance: the ability of a coating and the substrate it is protecting to resist damage or degradation due to water.

Water-based Coatings: these include latex paints, emulsion paints, and water paints. Coatings in which the volatile content is predominantly water.

Waterborne Coatings: see water-based coatings.

Waterproofing: treatment of a surface or structure to prevent the passage of water under hydrostatic pressure. Weather Resistance: the ability of a material, paint film, or the like to withstand effects of wind, rain, sun, etc., and retain its appearance and integrity.

Weathering: behavior of paint or coating films when exposed to natural, weather or accelerated weathering equipment, characterized by changes in color, texture, strength, chemical composition, or other properties.

Wet Adhesion: the ability of a coating film to adhere tightly to a substrate directly beneath it under wet conditions such as rain, dew, washing, etc.

Wet Edge: the edge of a wet, painted area which remains workable.

Wet Film Thickness: thickness of the liquid coating film immediately after application.

Whole-building Design: The integration of a building’s systems to maximize environmental and financial functioning by considering energy systems, building materials, design methods, site preservation, and indoor air quality so that a structure can run at its maximum efficiency.

Wind Uplift: the force caused by the deflection of wind at roof edges, roof peaks or obstructions, causing a drop in air pressure immediately above the roof surface. This force is then transmitted to the roof surface. Uplift may also occur because of the introduction of air pressure underneath the membrane and roof edges, where it can cause the membrane to balloon and pull away from the deck.

Zinc Oxide: ZnO a fine particle, white pigment used in rubber, paint, and plastic industries for mildew resistance and film reinforcing properties.