Glossary A-Z


• A-Side (A-Component): One component of a two component system. For polyurethane foam and coatings the isocyanate component.

• Absorption: Process whereby a porous material extracts one or more substances from an atmosphere, a mixture of gases, or a mixture of liquids.

• Acrylic Coating: A coating system based on an acrylic resin. Generally, a "water based" coating system that cures by coalescence and air-drying.

• Acrylics: Resins resulting from the polymerization of derivatives of acrylic acids, including esters of acrylic acid, methacrylic acid, acrylonitrile, and their copolymers. They can be carried in a water or solvent solution and they are film-forming materials.

• Adhesion: The degree of attachment or bonding of one substance to another. The degree of attachment or bonding between applications of the same substance.

• Adhesive: A substance or compound used for bonding surfaces together, usually applied in the form of a liquid or paste. An adhesive and sealant or base coat may be the same material.

• Aliphatic (Polyurethane): An organic polymer containing straight or branched chain arrangements of carbon atoms. As compared to aromatic urethanes, coatings based on aliphatic urethanes usually have better gloss, color retention, and weathering.

• Aromatic (Polyurethane): An organic polymer usually containing one or more benzene ring structures. Coatings are usually tougher and at a lower cost than aliphatics. As compared to aliphatic, coatings based on aromatic polyurethane's usually have tougher physical properties and cost less.

• Aromatic Solvents: Hydrocarbon solvents comprised of organic compounds, which contain an unsaturated ring of carbon atoms, including benzene, xylene, toluene and their derivatives.


• B-Side (B-Component): One component of a two component system. For polyurethane foam and coatings the resin component.

• Back Wrapping: The carrying of EIFS mesh reinforcement and base coat around the ends of the insulation boards and terminating between the insulation and substrate. Typically used at system interfaces and terminations to firmly attach the base coat to the substrate and protect the edges of the insulation board at these locations.

• Base Coat: The first coat of a multi-coat system. This should be applied the same day as the spray polyurethane foam.

• Bead: A line of sealant or adhesive. In glazing, an applied sealant in a joint such as caulking bead, heel bead, glazing bead, etc. Also a molding or stop used to hold glass or panels in position.

• Bleeding: (1) The diffusion of coloring matter through a coating from its substrate (such as bleeding of asphalt mastic through coating). (2) The absorption of oil or vehicle from a compound into an adjacent porous surface.

• Blister: An uplifting of coating or polyurethane foam caused by an enclosed pocket of gas or liquid entrapped between coating passes, foam and coating, foam and substrate, or within the foam itself. Caused by the delamination of one or two components in an insulation or roofing system.

• Bond (Chemical): Adhesion between surfaces, usually of similar materials, resulting from a chemical reaction or cross linking of polymer chains.

• Bond (Mechanical): Adhesion between surfaces resulting from interfacial forces or a physical interlocking.

• Butyl Coating: An elastomeric coating system derived from polymerized isobutylene. Butyl coatings are characterized by low water vapor permeability.


• Catalyst: An ingredient in a coating or polyurethane foam system that initiates a chemical reaction or increases the rate of chemical reaction.

• Cavitation: The vaporization of a liquid under the suction force of a pump. Usually due to inadequate flow to a pump; the vaporization can create voids within the pump of the pump supply line. In polyurethane foam spray pumps, cavitation will result in off-ratio foam.

• Caulking: Another term for sealant.

• CFM: abbreviation for Cubic Feet per Minute. A unit of volumetric flow rate, ofter used as a metric of ventillation, airflow, or air leakage.

• Coating: A layer of material applied over a surface for protection or decoration. Coatings for polyurethane foam are liquids, semi-liquids, or mastics; spray, roller or brush applied; and are elastomeric.

• Cream Time: The time, measured in seconds at a given temperature, when the polyurethane foam components will begin to expand after being mixed.

• Cure: To develop the ultimate properties of a wet state material by a chemical process. Different than drying, which is not a chemical process, although drying is often a necessary part of a chemical process.

• 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 or adhesive that increases the rate of cure.


• Delamination: The separation of layers within a material or materials. May result in a blister formation.

• Deliquescence: The process that occurs when the vapor pressure of the saturated aqueous solution of a substance is less than the vapor pressure of water in the ambient air. When water vapor is collected by the pure solid compound, a mixture of the solid and liquid, or an aqueous solution of the compounds forms until the substance is dissolved and is in equilibrium with its environment, at this time the vapor pressure of water over the aqueous solution with equal the partial pressure of water in the atmosphere in contract with it. Deliquescence is the revers of efflorescence.

• Dessicant: A drying agent.

• Dew Point: The temperature at which the relative humidity of a sample of air with constant water vapor reaches 100%. The air is saturated with water when it reaches the dew point and condensation will occur on a surface.

• Diisocyanate: An organic chemical compound having two reactive isocyanate (-N=C=O) groups; used in the production of polyurethane foams and coatings.

• Drying Time: The time required for the material to become tack free and will no longer be adversely affected by weather phenomena such as dew, rain or freezing.

• Durability: The capability of a building, assembly, component, product or building to maintain serviceability over a specified time.


• Elastomer: A material which at room temperature is capable of being stretched repeatedly at least twice its original length 100% elongation and, upon release of stress, will return to its original dimensions.

• Emulsion: A colloidal dispersion of one liquid in another. (See Latex; Colloidal Dispersion)

• Epoxy: A class of synthetic, thermosetting resins, which produce tough, hard, chemical-resistant coatings and adhesives.

• Expansion Joint: A structural separation between building elements that allows independent movement without damage to the assembly.

• Exotherm: Heat generated by a chemical reaction.


• Fast Set: A coating system with a very fast initial cure time, usually five seconds to one hour.

• Feathered Edge: The thin tapered outside edge of a polyurethane foam pass.

• Filler: A relatively inert ingredient added to coating or polyurethane foam formulations to modify physical characteristics.

• Finish Coat: The coating applied to the base coat to finish the lamina of an EIFS. The finish coat provides color. texture, water protection, dirt resistance and ultra violet ray resistance.

• Fire Resistance: The ability of a building component to resist the spread of fire.

• Flame-Retardant: A substance that is added to a coating or polyurethane foam formulation to reduce or retard its tendency to burn.

• Flash Coat: A thin initial pass of a spray-applied material.

• Foam Stop: The roof edge treatment upon which polyurethane foam is terminated.

• Friability: The tendency of a material or product to crumble or break into small pieces easily.


• Glass Eye or Glass Windows: Thin clear membrane that forms over elongated polyurethane foam cells. Glass eyes may break when coated, forming a pinhole.

• Gloss: The shine, sheen, or luster of a dried film.

• Granule: Size No. 11 ceramic aggregate embedded into wet coating over polyurethane foam for aesthetics, traction, and mechanical resistance.


• Hardness: Measure of how resistant solid matter is to various kinds of permanent shape change when a force is applied.

• HCFC: Hydrochloroflurocarbon. A second generation blowing agent for polyurethane foam.

• Heat Sink: A cold substrate that absorbs the SPF exothermic heat, slowing down the reaction and/or rise of the polyurethane foam or coating.


• ICAA: Insulation Contractors Association of America.

• Impact Resistance: Ability to withstand mechanical or physical blows without the loss of protective properties. The impact resistance of the roofing assembly is a function of all its components not just the membrane itself.

• Insulation: (Thermal) Any material which significantly slows down or retards the flow or transfer of heat. Building insulation types are classified according to form (e.g. loose-fill, batt, flexible, rigid, reflective, and foamed-in-place) or material (mineral fiber, organic fiber, foam plastic). All types are rated according to their ability to resist heat flow (R-Value or RSI). (Electrical) A non-conductive wire covering, often rubber, thermoplastic, or asbestos. The thickness of insulation varies with wire size and type of material, application or other code limitations.

• Isocyanate: A highly reactive organic chemical containing one or more isocyanate (-N=C=O) groups. A basic component in polyurethane foam chemical systems and some polyurethane coating systems.


• Joints: An interface between elements. Joints may be needed to allow for movement of different parts of a building or assembly, or may be required to make construction sequences practical. In all cases, the functional requirements of the enclosure must be maintained the same as for the body of an enclosure element, although aesthetic requirements may be relaxed. A joint may pass through the entire enclosure assembly, in which case it is a building movement or assembly joint, often commonly (and imprecisely) referred to as an expansion joint. Control joints are surface cuts or intentional geometric features which control the location of shrinkage cracks. Construction joints are formed between successive building element parts during construction work.


• K-Factor: Thermal conductivity for a unit thickness of material. Expressed as W/m.ºK (ºF). R-value is equal to the thickness of the material divided by the k-factor (R=x/k where x=thickness).

• Knit Line or Lift Line: Interchangeable terms describing the adhesion plane where one pass is sprayed over another.

• Krebs Units (KU): A measurement of viscosity for materials that have the property of changing resistance to flow when under shear. Such materials are called thixotropic. Measuring is done with a Krebs/Stormer viscometer.


• Latex: A colloidal dispersion of a polymer or elastomer in water that coalesces into a film upon evaporation of the water.

• Lift: The sprayed polyurethane foam that results from a pass.

• Low Temperature Flexibility: The ability of a membrane or other material to remain flexible (resist cracking when flexed), after it has been cooled to a low temperature.

• Low-Density SPF Insulation: SPF having a nominal density of less than one pound per cubic foot and used primarily as an insulation and air seal. Relative to medium-density SPF, typically Low-Density SPF Insulation is characterized by having a lower closed-cell content, higher water vapor permeance, and higher yields. Most Low-Density Insulations use water as a reactive blowing agent and are considered non-structural.

• Low Temperature Flexibility: The ability of a membrane or other material to remain flexible (resist cracking when flexed), after it has been cooled to a low temperature.


• Maintenance: A regular process of inspection, cleaning and minor repairs of buildings elements and exterior systems. Cleaning is for normal activities for those items as required on a regular basis, such as leaves from gutters and drains in the fall, and cleaning lint from dryer vents. Minor repairs encompass small projects that reinstate failed elements such as areas of cracked caulking or peeling paint.

• Material Safety Data Sheet (MSDS): A standard formatted information sheet prepared by a material manufacturer which describes the potential hazards, physical properties, and procedures for safe use of a material.

• Membrane: A flexible or semi-flexible roof covering whose primary function is the exclusion of water.

• Methylene Diphenyl Diisogyanate (MDI): Component A in spray polyurethane foam. An organic chemical compound having two reactive

isocyanate (-N=C=O) groups. It is mixed with the B component to form polyurethane

• Micron: One inch equals 25,400 microns (100 microns = 0.0039 mils)

• Mil: One-thousandth of an inch; 0.001 inch (0.025mm). A unit used to measure coating thickness.

• Monolithic: Formed from or composed of a single material; seamless.


• Neoprene Rubber - A synthetic rubber having physical properties closely resembling those of natural rubber. Made by polymerization of


• Night Seal - A material and or method used to temporarily seal a membrane edge during construction to protect the roofing assembly in

place from water penetration. May be removed when roofing application is resumed.

• Non-Breathing Membrane - A membrane material that has a significantly greater resistance to the diffusion of water vapor than the other materials with which it is used.

• Non-Ferrous Metal - All metals that are not iron compounds, i.e., copper, lead, gold, silver, and aluminum. These metals are non-magnetic.

• Non-Flammable - Liquid having no measurable flash point.

• Non-Oxidizing - A material that resists oxidation in exterior exposures or accelerated weathering.

• Non-Volatile Content - That portion of a coating material that does not evaporate under normal ambient conditions. (For Comparison See SOLIDS CONTENT)

• NRCA - National Roofing Contractors Association.


• Off-Ratio Foam - Polyurethane which has a lack of isocyanate or resin. Off-ratio foam will not exhibit the full physical properties of normal foam.

• Orange Peel Surface Texture - The surface texture of polyurethane foam resembling that of an orange peel.

• Organic - Compounds containing carbon.

• Orifice - An opening or aperture. The opening in the tip of a spray gun.

• Overspray - (1) Airborne spray loss of polyurethane foam or coatings.

(2) Undesirable depositions of airborne spray loss.

• Overspray Surface Texture - The surface shows a linear coarse textured pattern and/or a pebbled surface. This surface is generally downwind of the sprayed polyurethane path and is unacceptable for proper coating coverage and protection, if severe.


• Pass - The amount of coating or polyurethane foam applied by moving the gun from side to side and moving away from fresh material. A pass is delineated by its width, length and thickness.

• Pass Lines - The overlapping of the polyurethane foam or coating as the newly applied material ties into the previous pass.

• Peel Strength - The average force (or force per unit width) required to peel a membrane or other material from the substrate to which it has been bonded.

• Peeling - Top-coating film inadequately bonded with undercoats resulting in partial delamination or detachment of final coat.

• Personal Protective Equipment (PPE) - Specialized clothing or equipment worn by employees for protection against health and safety hazards. Personal protective equipment is designed to protect many parts of the body, i.e., eyes, head, face, hands, feet and ears.

• pH - A measure of acidity/alkalinity of aqueous mixtures. A measure of pH 7 is neutral, lower is more acidic, higher is more alkaline.

• Pigment - Fine solid particles dispersed in a coating to impart color.

• Pinhole - A small hole in a mastic, coating, or polyurethane foam.

• Plasticizer - A substance added to a plastic or coating to increase its flexibility or elongation.

• Polymer - A substance consisting of high molecular weight chemical compounds characterized by chains of repeating simpler units.

• Polyol - Polyol is the main ingredient of the resin component that reacts with the isocyanate to form polyurethane.

• Polyurethane Coatings - A one or two part coating that contains polyisocyanate monomer and a hydroxyl containing resin, which react during cure to form polyurethane elastomeric.

• Polyurethanes - A compound based on the reaction of various isocyanates and various polyol resins. These compounds or polymers can create rigid foams, flexible foams, elastomeric coatings or structural resins and many other forms. They are either an aromatic or aliphatic polyurethane.

• Primer - The first layer of coating applied to a surface to improve the adhesion of subsequently applied materials or to inhibit corrosion.

• Proportioner - The basic pumping unit for spraying polyurethane foam or two component coating systems. Consists of two positive displacement pumps designed to dispense two components at a precisely controlled ratio.

• PSI - Pounds per square inch.

• Psychrimeter - A device for measuring ambient humidity by employing a dry bulb thermometer and a wet bulb thermometer.

• Purge - To cleanse or remove liquid materials from equipment or hoses.


• QUV - An apparatus used to simulate the effects of weathering of materials.


• R Value - The resistance of a material to heat transfer. Insulators have relatively high R values. Units are °K·m2/W (°F·ft2·hr/Btu).

• Relative Humidity - The ratio of absolute humidity to saturation humidity, expressed as a per cent.

• Resin - (1) Component B in SPF. This component contains a polyol catalyst, blowing agent, fire retardant, and surfactants. It is mixed with the A component to form polyurethane.

(2) General term applied to a wide variety of more or less transparent and fusible products, which may be natural or synthetic. Higher molecular weight synthetic resins are referred to as polymers.
(3) Any polymer that is a basic material for coatings and plastics.

• Rigid Insulation - Rigid board material that provides thermal resistance. Foam plastic such as EPS, XPS, and polyisocyanurate are commonly used.

• Retrofit - The modification of an existing building or facility to include new systems or components.


• Saddle - A relatively small raised substrate or structure constructed to channel or direct surface water to drains or off the roof. A saddle may be located between drains or in a valley, and is often constructed like a small hip roof or like a pyramid with a diamond-shaped base. (See CRICKET) SAG: Undesirable excessive flow or run in material after application to a sloped or vertical surface.

• Scarf - To remove the surface or coating from polyurethane foam by cutting, grinding, or other mechanical means. Synonymous with SCARIFY.

• SCV - Solid content by volume.

• Sealant - Any of a variety of compounds used to fill and seal joints or openings in wood, metal, masonry and other construction materials. Some common types of sealants are Neoprene®, polysulfide, acrylic latex, butyl, polyurethane, foams and silicone.

• Sealant Foam - One or two component polyurethane foam applied as a bead and used to control air leakage as part of an air barrier system within the building envelope.

• Shelf Life - The period of time within which a material remains suitable for use. Synonymous with STORAGE LIFE.

• Solvent - A liquid that dissolves other substances

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

• Spray Polyurethane Foam (SPF) - A foamed plastic material formed by the reaction of an isocyanate and a polyol and employing a blowing agent to develop a cellular structure. SPF may be a two-component reactive system mixed at a spray gun or a single-component system that cures by exposure to moisture. SPF can be formulated to have physical properties (such as density, compressive strength, closed cell content, and R-value) appropriate for the application requirements. Common uses of SPF include insulation, air barrier and roofing membrane.


• Tear Strength - The maximum force required to tear a specimen, the force acting substantially parallel to the major axis of the test specimen. Values reported as a stress per unit of thickness.

• Tensile Strength - The tensile (pulling or stretching) force necessary to rupture a material sample divided by the sample’s original cross sectional area. Units are usually kPa or psi or lb/in2.

• Thermoset - A polymeric material whose physical properties are relatively unaffected by modest changes in temperature; when heated, thermosets will degrade rather than melt.

• Thinner - A liquid used to reduce the viscosity of coatings or mastics. Thinners evaporate during the curing process. Thinners may be used as solvents for clean up of equipment.

• Toxicity - The quality, property, or degree of being poisonous or toxic.

• Two-Part System - A coating or polyurethane foam formed by the mixing and the reaction of two different materials.


• U Value - Overall thermal conductance. U value is equal to the inverse of the sum of the R-values in a system (U = 1/R total). Units are °K·m2/W (°F·ft2·hr/Btu).

• UBC - Uniform Building Code. Model building code generated by ICBO.

• Underlayment - A material that is laid down as a substrate for the sprayed polyurethane foam to make the surface smooth or to give a specific rating for interior fire exposures.

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


• Viscosity - The thickness or resistance to flow of a liquid. Viscosity generally decreases as temperature increases.

• Ventilation - The intentional flow of air into occupied spaces or behind cladding/roofing to move heat and moisture in a desirable manner.

• Volatile Organic Compounds (VOC) - Any compound containing carbon and hydrogen or containing carbon and hydrogen in combination with other elements that has a vapor pressure of 1.5 pounds per square inch absolute (77.6 mm Hg) or greater under actual storage conditions.


• Water Absorption - The percent increase in weight of a specimen after contact with water for a specified time.

• Wet Film Thickness - The thickness, expressed in mm or mils, of a coating or mastic as applied but not cured.