: 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. 


SATURATION HUMIDITY: The maximum concentration of water vapor in the air at a given temperature before condensation occurs. 

SBCCI: Southern Building Code Congress International. SBCCI, once one of three model code agencies in the United States, developed the Southern Building Code, which had been commonly adopted in the Southern U.S. SBCCI has been absorbed into the ICC. (See also INTERNATIONAL CODE COUNCIL.)

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


SCRIM: A woven, non-woven, or knitted fabric, composed of continuous strands of material used for reinforcing or strengthening membranes. Scrim may be incorporated into a membrane by the laminating or coating process. 

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

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 typically applied as a bead and used to control air leakage as part of an air barrier system within the building envelope. Sealant foams generally have nominal core densities of 8–40 kg/m3 (0.5–2.5 lb/ft3).

SELF-FLASHING: The ability of sprayed polyurethane foam to be applied around a penetration or at a roof transition without the need for other materials. 

SERVICE TEMPERATURE LIMITS: The maximum continuous temperature at which a coating, polyurethane foam, or other material will perform satisfactorily. 

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

SET OF FOAM: A container of A-side (MDI) and a container of B-side (polyol or resin blend) that can be combined through mixing equipment to form SPF. A set of foam consists of two containers, typically 55-gallon drums.

SHELF LIFE: The period of time within which a material remains suitable for use. Synonymous with STORAGE LIFE. 

SHORE HARDNESS: A measure of hardness based on the Shore scale. 

SILICONE COATING: A liquid-applied, solvent dispersed, elastomeric protective coating whose principal polymer in the dispersion contains more than 95% silicone resin. Some high-solids silicone coatings may have little or no solvent content.

SINGLE-COMPONENT FOAM: A fully formulated foam system packaged in a single aerosol can or pressurized cylinder. Essentially a moisture cure polyurethane prepolymer in a pressurized container. Also called One-Component Foam or OCF.

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

SLIT SAMPLES: Small cut samples approximately 2 in. long, 1/2 in. wide, and 3/4 in. deep that are taken for evaluation of sprayed materials. 

SMOKE DEVELOPED: The amount of smoke measured for a sample tested in the ASTM E 84 tunnel test when compared to inorganic reinforced cement board and select-grade red-oak flooring, which have been arbitrarily established as 0 and 100, respectively.

SMOOTH SURFACE TEXTURE: The surface texture of SPF that exhibits spray undulation and is ideal for receiving a protective coating. Even though the surface texture is classified as smooth, this surface requires at least 5% additional coating material to the theoretical amount. (See SPFA-145, “Surface Texture of Spray Polyurethane Foam.”)

SOCIETY OF THE PLASTICS INDUSTRY: A trade association representing the interests of the plastics industry.

SOLAR REFLECTANCE: The measure of a surface material’s ability to scatter sunlight. COOL ROOFS and reflective coatings typically have a high solar reflectance. Also termed “albedo.” (See also COOL ROOFS.)

SOLAR REFLECTANCE INDEX (SRI): A calculated index (0–100+ based on ASTM E 1980) that combines a surface material’s solar reflectance and infrared emittance into a single value. The SRI provides a relative indication of how hot a surface material will become when exposed to sunlight. Cool surfaces have high index values, while hot surfaces have low index values.

SOLIDS CONTENT: The percentage of non-volatile matter in a coating or mastic formulation; may be expressed as a volume or weight percent. 

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

SOUND TRANSMISSION CLASS (STC): An integer rating of how well a building partition reduces airborne sound. STC is widely used to rate interior partitions, ceilings/floors, doors, windows, and exterior wall configurations.


SPI / SPFD: The Society of the Plastics Industry / Spray Polyurethane Foam Division. From 1987 to 1999, SPFA was known as SPFD a division of SPI. In 1999, SPFA became an independent trade association, with strong collaborative relationships with the American Chemistry Council’s (ACC’s) Center for the Polyurethanes Industry (CPI), Insulation Contractors Association of America (ICAA), and the National Roofing Contractors Association (NRCA). 


SPF, HIGH PRESSURE: Spray polyurethane foam where the A- and B-components are delivered at a pressure between 1000 and 1300 psi, at a rate up to 30 lb/min wherein the components are atomized and impingement mixed in a spray gun.

SPF, LOW PRESSURE: Spray polyurethane foam where the A- and B- components are delivered a pressure of less than 250 psi, at a rate between 5 and 7 lb/min wherein the components are mixed using a static mixing nozzle. Components are typically delivered in pressurized tanks.

SPFA: Spray Polyurethane Foam Alliance.

SPFA DOCUMENTS: Technical and informational documents published by the Spray Polyurethane Foam Alliance (SPFA) for use by members and distribution to the public. Documents are numbered “SPFA-XXX.” (Previous documents were designated “AY,” which was developed as part of a numbering system by the Society of the Plastics Industries.)

SPRAY POLYURETHANE FOAM (SPF): A foamed plastic material formed by the reaction of an isocyanate and a polyol, and by employing a blowing agent to develop a cellular structure. Spray polyurethane foam, 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 appropriate for the application requirements, such as density, compressive strength, closed cell content, and R-Value. Common uses of SPF include insulation, air barrier, roofing membrane and geotechnical applications. 

SPUD: To remove the roofing aggregate and most of the bituminous top coating by scraping and chipping. 

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


STACK EFFECT: Also referred to as the “chimney effect,” stack effect results from air density differences between building interiors and exteriors. During heating seasons, the stack effect results in higher relative pressures at the tops of buildings and lower relative pressures at the bases of buildings. These pressure differences can drive air infiltration/exfiltration. Proper sealing measures, such as air barriers formed by SPF and sealants, can mitigate stack effect.



STRESS: An applied force that tends to deform a body. May be tensile stress (pulling or stretching force), compressive stress (pushing or compacting force), or shear stress (opposite, but offset parallel forces tending to produce a sliding motion). 

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

SUBSTRATE: The surface to which polyurethane foam is applied. 

SUPPLIED-AIR RESPIRATOR (SAR): Often referred to as an airline respirator. These devices provide air to the user, through an airline, from a source located some distance away. (See RESPIRATOR.)

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

SURFACE TEXTURE: The resulting surface from the final pass of SPF. The following terms are used 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 underlying roofing from direct exposure to the weather. 

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

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