Glossary of Roofing Terms

Open Time: the period of time after an adhesive has been applied and allowed to dry, during which an effective bond can be achieved by joining the two surfaces.

Open Valley: a method of valley construction in which the steep-slope roofing on both sides are trimmed along each side of the valley, exposing the valley flashing.

Orange Peel Surface Texture: the surface shows a fine texture and is compared to the exterior skin of an orange. This surface is considered acceptable for receiving a protective coating. The theoretical coverage rate cannot be used without adding a minimum 10% additional material to adequately cover the orange peel texture.

Organic: being or composed of hydrocarbons or their derivatives originating from plant or animal matter.

Organic Felt: an asphalt roofing base material manufactured from cellulose fibers.

Organic Shingle: an asphalt shingle reinforced with material manufactured from cellulose fibers.

Osmosis: the diffusion of fluids through a semi-permeable membrane or porous partition.

Overspray: 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. The minimum percentage of additional material to be added will vary from 25% to 50% depending upon the type of surface texture.

Ozone Resistance: the ability of a material to resist the deteriorating effects of ozone exposure.

Pallet: a platform (typically wooden) used for storing and shipping materials.

Pan: the bottom flat part of a roofing panel which is between the ribs of the panel.

Pan Former: power roll-forming equipment that produces a metal roofing panel from a flat sheet.

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

Parge: in masonry construction, a coat of cement mortar on the face of rough masonry, the earth side of foundation and basement walls, or the like.

Partially-Attached: a roofing assembly in which the membrane has been "spot affixed" to a substrate, usually with an adhesive or a mechanical device.

Pass: 1) a layer of material, usually applied by the spray method, that is allowed to reach cure before another layer (pass) is applied; 2) a term used to explain a spray motion of the foam gun in the application of the spray polyurethane foam (SPF) material. The speed of the "pass" controls the thickness of the SPF.

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.

Penetration: (1) any object passing through the roof; (2) the consistency (hardness) of a bituminous material expressed as the distance, in tenths of a millimeter (0.1 mm), that a standard needle penetrates vertically into a sample of material under specified conditions of loading, time, and temperature.

Percent Elongation: in tensile testing, the increase in the gauge length of a specimen measured at or after fracture of the specimen within the gauge length. Usually expressed as a percentage of the original gauge length.

Perlite: an aggregate used in lightweight insulating concrete and in preformed perlitic insulation boards, formed by heating and expanding siliceous volcanic glass.

Perm: a unit of water vapor transmission defined as 1 grain of water vapor per square foot per hour per inch of mercury pressure difference (1 inch of mercury = 0.49 psi). The formula for perm is: P = Grains of Water Vapor/Square Foot.Hour~lnch Mercury (P = grain~in/ft2.h~in Hg [P = ng/(Pa~s~m)]).

Permeability: (1) the capacity of a porous material to conduct or transmit fluids; (2) the amount of a fluid moving through a barrier in a unit time, unit area, and unit pressure gradient not normalized for, but directly related to, thickness.

Permeance: the rate of water vapor transmission per unit area at a steady state through a material, membrane or assembly, expressed in Grain/Square Foot.Hour~lnch Mercury (grain/ft2.h~in Hg [ng/Pa~a~m2]).

Phased Application: the installation of separate roof system or waterproofing system component(s) during two or more separate time intervals. Application of surfacings at different time intervals are typically not considered phased application. (See Surfacing.)

Picture Framing: a square or rectangular pattern of buckles or ridges in a roof covering generally coinciding with insulation or deck joints; generally, a function of movement of the substrate.

Pinhole: a tiny hole in a coating, film, foil, membrane, or laminate.

Pipe Boot: prefabricated flashing piece used to flash around circular pipe penetrations.

Pitch: see Coal Tar, Incline, and Roof Slope.

Pitch-Pocket (Pitch-Pan): a flanged, open bottomed enclosure made of sheet metal or other material, placed around a penetration through the roof, filled with grout and bituminous or polymeric sealants to seal the area around the penetration.

Pittsburgh Lock Seam: a method of interlocking metal, usually at a slope change.

Plastic Cement: a roofing industry generic term used to describe Type I asphalt roof cement that is a trowelable mixture of solvent-based bitumen, mineral stabilizers, other fibers and/or fillers. Generally, intended for use on relatively low slopes - not vertical surfaces. (Also see Asphalt Roof Cement and Flashing Cement.)

Plastic Film: a flexible sheet made by the extrusion of thermoplastic resins.

Plasticizer: a material, frequently solvent-like, incorporated in a plastic or a rubber to increase its ease of workability, flexibility, or extensibility.

Plastomeric: a plastic-like polymer consisting of any of various complex organic compounds produced by polymerization, and capable of being molded, extruded, or cast into various shapes or films.

Pliability: the material property of being flexible or moldable.

Ply: a layer of felt, ply sheet, or reinforcement in a roof membrane or roof system.

Polyester: a polymeric resin which is generally cross-linked or cured and made into a variety of plastic materials and products. Polyester fibers are widely used as the reinforcing medium in reinforced membranes. (See Polyester Fiber.)

Polyester Fiber: a synthetic fiber usually formed by extrusion. Scrims made of polyester fiber are used for fabric reinforcement.

Polymer: a natural or synthetic chemical compound of high molecular weight, or a mixture of such compounds, formed when monomers (small individual molecules) are combined to form large long-chain molecules.

Polymer Modified Bitumen: See Modified Bitumen.

Polypropylene: a tough, lightweight plastic made by the polymerization of high-purity propylene gas.

Polyvinyl Chloride (PVC): a synthetic thermoplastic polymer prepared from vinylchloride. PVC can be compounded into flexible and rigid forms through the use of plasticizers, stabilizers, fillers, and other modifiers; rigid forms are used in pipes; flexible forms are used in the manufacture of sheeting and roof membrane materials.

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

Pop Rivet: a relatively small headed pin with an expandable head for joining relatively light gauge metal.

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.

Positive Side Waterproofing: an application where the waterproofing systems and the source of the hydrostatic pressure are on the same side of the structural element.

Pourable Sealer: a type of sealant often supplied in two parts, and used at difficult-to-flash penetrations, typically in conjunction with pitch-pockets to form a seal.

Pre-Tinning: coating a metal with solder or tin alloy, prior to soldering or brazing it.

Press Brake: a machine used in cold-forming sheet metal or strips of metal into desired profiles.

Prestressed Concrete: concrete in which the reinforcing cables, wires, or rods in the concrete are tensioned before there is load on the member, holding the concrete in compression for greater strength.

Primer: (1) a thin, liquid-applied solvent-based bitumen that may be applied to a surface to improve the adhesion of subsequent applications of bitumen; (2) a material which is sometimes used in the process of seaming single-ply membranes to prepare the surfaces and increase the strength (in shear and peel) of the field splice.

Protected Membrane Roof (PMR): an insulated and ballasted roofing assembly, in which the insulation and ballast are applied on top of the membrane (sometimes referred to as an "inverted roof assembly").

Puncture Resistance: extent to which a material is able to withstand the action of a sharp object without perforation.

Purlin: horizontal secondary structural member that transfers loads from the primary structural framing.

PVC: Polyvinyl Chloride.

R-Value: the resistance to heat transfer of a material. Insulators have relatively high R values. Units are °F.Ft2.Hr/Btu.

Racking: a method of asphalt shingle application, also referred to as the straight-up method, whereby shingle courses are applied vertically, up the roof rather than laterally or across and up.

Rafter: one of a series of sloped structural members, that extend from the ridge or hip to the downslope perimeter or cave, designed to support the roof deck and its associated loads. (See Figure 19.)

Raggle: a groove or slot, often cut in a masonry wall or other vertical surface adjoining a roof, for inserting an inset flashing component such as a regret.

Rake: the sloped edge of a roof at or adjacent to the first or last rafter. (See Figure 20.)

Rake-Starter (Bleeder Strip): starter-strip used along rake edges in conjunction with asphalt shingle roofing.

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.

Reflectivity: see Light Reflectance.

Reglet: a sheet metal receiver for the attachment of counterflashing. (A regret may be inset into a raggle, embedded behind cladding, or be surface mounted.)

Reinforced Membrane: a roofing or waterproofing membrane that has been strengthened by the addition or incorporation of one or more reinforcing materials, including woven or nonwoven glass fibers, polyester mats or scams, nylon, or polyethylene sheeting.

Relative Humidity: the ratio of the weight of moisture in a given volume of air-vapor mixture to the saturated (maximum) weight of water vapor at the same temperature, expressed as a percentage. For example, if the weight of the moist air is 1 pound and if the air could hold 2 pounds of water vapor at the same temperature, the relative humidity (RH) is 50 percent.

Release Tape (or Strip): a plastic film or paper strip that is applied to the back of self-sealing shingles and other materials. The strip prevents the material from sticking together in the roll or bundle. With asphalt shingles, the strip need not be removed for application of the shingles.

Replacement: the practice of removing an existing roof system down to the roof deck and replacing it with a new roofing system.

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

Resin: component B in SPF. This component contains a catalyst, blowing agent, fire retardants, surfactants and polyol. It is mixed with the A component to form polyurethane.

Resistance, Thermal: the average temperature difference between two defined surfaces of a particular body or assembly when unit thermal transmission in unit time through unit area is established between the surfaces. R=°F.h~s~ft2/Btu (R=K.m2NV).

Ridge: highest point on the roof, represented by a horizontal line where two roof areas intersect, running the length of the area. (See Figure 21.)

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

Ridge Course: the last or top course of roofing materials, such as tile, roll roofing, shingles, etc., that covers the ridge and overlaps the intersecting field roofing.

Ridge Vent: a ventilator located at the ridge that allows the escape of warm and/or moist air from the attic area or rafter cavity. Most ridge vents are either premanufactured metal or flexible, shingle-over type.

Ridging: see Buckle.

Roll Goods: a general term applied to rolls of roofing felt, ply sheet, etc., which are typically furnished in rolls.

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 or Roofer's Cement: see Asphalt Roof Cement or Coal Tar Roof Cement.

Roof Covering: the exterior roof cover or skin of the roof assembly, consisting of membrane, panels, sheets, shingles, tiles, etc.

Roof Curb: raised frame used to mount mechanical units (such as air conditioning or exhaust fans), skylights, etc.

Roof Diaphragm: a structural roof deck that is capable of resisting shear that is produced by lateral forces, such as wind or seismic loads.

Roof Jack: a metal bracket used to support toe-boards on steep-slope roofs. (Also see Flashing Collar.)

Roof Overhang: a roof extension beyond the exterior wall of a building.

Roof Seamer: machine that crimps neighboring metal roof panels together, or that welds laps of membrane sheets together using heat, solvent, or dielectric energy.

Roof Slope: the angle a roof surface makes with the horizontal, expressed as a ratio of the units of vertical rise to the units of horizontal length (sometimes referred to as run). For English units of measurement, when dimensions are given in inches, slope may be expressed as a ratio of rise to run, such as 4:12, or as a percent.

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.

Roofer: craftsman who applies roofing materials.

Rosin Paper (specifically Rosin-Sized Sheathing Paper): a non-asphaltic paper used as a sheathing paper or slip sheet in some roof systems.

Rubber: a polymeric material which, at room temperature, is capable of recovering substantially in shape and size after removal of a force. May be natural or synthetic.

Run: horizontal dimension of a slope.

  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 in material after application to a surface.

Saturated Felt: a felt that has been partially saturated with low softening point bitumen.

Screeding: the process of striking off excess concrete to bring the top surface of the concrete to the proper finish and elevation.

Screen Wall: a nonstructural wall erected around units or curbs on a roof. Typically the framing consists of girts with a wood or metal covering attached to the frame.

Scrim: a woven, nonwoven, 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.

Scuttle: a hatch that provides access to the roof from the interior of the building.

Seal: (1) a generic term for a function that prevents or controls the passage of water; (2) to secure a roof or structure from the entry of moisture.

Sealant: a single- or multi-component polymeric or bituminous-based material used to weatherproof many types of construction joints where moderate movement is expected. The material comes in various grades: pourable, self-leveling, non-sag, gun grade, and cured or uncured tapes.

Sealer: a coating designed to prevent absorption of finish coats into porous surfaces; a coating designed to prevent bleeding.

Sealing Washer: a rubber or neoprene washer, sometimes metal-backed, typically assembled on a fastener to prevent water from migrating into and through the fastener hole.

Seam: a joint formed by mating two separate sections of material. Seams may be made or sealed in a variety of ways, including adhesive bonding, hot-air welding, solvent welding, using adhesive tape, sealant, etc.

Seam Strength: the force or stress required to separate or rupture a seam in the membrane material.

Self-Adhering Membrane: a membrane that can adhere to a substrate and to itself at overlaps without the use of an additional adhesive. The undersurface of a self-adhering membrane is protected by a release paper or film, which prevents the membrane from bonding to itself during shipping and handling.

Self-Drilling Screw: a fastener that drills and taps its own hole during application.

Self-Sealing Shingle: an asphalt shingle containing factory-applied strip or spots of heat sensitive adhesive intended to adhere the overlying shingle once installed on the roof and warmed by the sun.

Self-Tapping Screw: a fastener that forms receiving threads when turned into a previously drilled hole.

Self-Vulcanized Membrane: a membrane manufactured from compounds that are thermoplastic during manufacture and installation, but whose polymers eventually cross-link and cure during exposure.

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

Selvage Edge: an edge designed for certain sheet good materials, e.g., mineral-surfaced sheets. With mineral surfaced sheets, the surfacing is omitted over a portion of the longitudinal edge of the sheet (e.g., mineral surface cap sheet) in order to obtain better adhesion of the overlapping sheet.

Service Temperature Limits: the minimum or maximum temperature at which a coating, SPF, or other material will perform satisfactorily.

Shading: slight differences in surfacing color, such as shingle granule coloring, that may occur as a result of manufacturing operations.

Shark Fin: an upward-curled felt side lap or end lap.

Shear Strength: (in roofing) the stress required to disrupt a seam or bonded joint or attachment by forcing the substrate material to slide out from the overlying material or vice versa.

Shed Roof: a roof containing only one sloping plane. Has no hips, ridges, or valleys. (See Figure 22.)

Sheet Metal Flashing: see Metal Flashing.

Shelf Life: the period of time within which a material such as coating or SPF components remain suitable for use.

Shingle: (1) individual unit of prepared roofing material designed for installation with similar units in overlapping rows or courses on inclines normally exceeding 3:12 slope (25%); (2) to cover with shingles; (3) to apply any roofing material in succeeding overlapping rows or courses similar to shingles.

Shingling: (1) the application of shingles; (2) the procedure of applying shingles or laying parallel felts so that one longitudinal edge of each felt overlaps and the other longitudinal edge of the adjacent shingle or felts underlaps. Felts are normally shingled from a downslope portion of the roof to the upslope portion of the roof area so that runoff water flows over rather than against each felt lap. Felts are also applied in shingle fashion on relatively low slopes.

Shrinkage: a reduction in size.

Shrinkage Crack: in waterproofing, a separation in a material, like a concrete substrate, caused by the inability of the material to resist a reduction in size which occurs during its hardening process, curing process, or both.

Side Lap: the continuous longitudinal overlap of neighboring like materials. (See Figures 23 and 24.)

Side Lap Fastener: a fastener used to connect adjacent panels together at the side lap.

Side Lap-Ganging: pattern or application for roofing materials, as related to the amount of cover or side overlap of adjacent like materials.

Siding: the exterior wall finish material applied to a light frame wood structure.

Sieve: an apparatus with uniform sized openings for separating sizes of material.

Silicone-based Water Repellants: any of the organopolysiloxanes (silicone derivative) applied to masonry materials for dampproofing or repelling water.

Sill: the bottom horizontal framing member of an opening, such as below a window or door.

Sill Flashing: a flashing of the bottom horizontal framing member of an opening, such as below a window or door.

Single Coverage: roofing material that provides one layer over the substrate to which it is applied.

Single-Lock Standing Seam: a standing seam that utilizes one overlapping interlock between two seam panels, in contrast with the double interlocking used in a double standing seam.

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 thermoses, thermoplastic, or polymer modified bituminous compounds.

Single-Ply System: generally, there are six types of single-ply roofing systems:

1) Fully-adhered

2) Loose-laid

3) Mechanically-fastened

4) Partially-adhered

5) Protected membrane roof

6) Self-adhering

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

Skylight: a roof accessory, set over an opening in the roof, designed to admit light. Normally transparent, and mounted on a raised framed curb.

Slag: a hard, air-cooled aggregate that is left as a residue from blast furnaces, which may be used as a surfacing material on certain (typically bituminous) roof membrane systems.

Slate: a hard, brittle metamorphic rock consisting mainly of clay minerals, used extensively as dimensional stone for steep roofing, and in granular form as surfacing on some other roofing materials.

Slating Hook: a steep-slope roofing attachment device, shaped like a hook, that can be used for fastening roofing slate.

Slip Sheet: sheet material, such as reinforced kraft paper, rosin-sized paper, polyester scrim, or polyethylene sheeting, placed between two components of a roof assembly (such as between membrane and insulation or deck) to ensure that no adhesion occurs between them, and to prevent possible damage from chemical incompatibility, wearing, or abrasion of the membrane.

Slope: the angle of incline, usually expressed as a ratio of rise to run, or as a percent. (See Roof Slope.)

Smooth Surface Texture: the surface shows spray undulation and is ideal for receiving a protective coating. Even though the surface texture is classified as smooth, the theoretical coverage rate cannot be used without adding a minimum of 5% additional material to adequately cover the undulation.

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

Snap-On Cap: a separate cap that snaps on over the vertical legs of some single standing or batten seam metal roof systems.

Snow Guard: a series of devices attached to the roof in a pattern that attempts to hold snow in place, thus preventing sudden snow or ice slides from the roof.

Snow Load: a load imposed on buildings or other structures due to snowfall. (Categorized as live or environmental load.)

Soffit: the enclosed underside of any exterior overhanging section of a roof cave.

Soffit Vent: a premanufactured or custom built air inlet source located at the downslope eave or in the soffit of a roof assembly.

Softening Point: the temperature at which bitumen becomes soft enough to flow, as determined by a closely defined method (ASTM Standard test method D 36 or D 3461).

Softening Point Drift: a change in the softening point of bitumen. (See Fallback.)

Soil Stack: a sanitation pipe that penetrates the roof; used to vent plumbing fixtures.

Solder: a lead/tin mixture that is melted and used to bond two pieces of some metals together.

Solid Mopping: see Mopping.

Solvent: liquid used to dissolve or disperse film-forming constituents, and which evaporates during drying and does not become a part of the dried film.

Solvent Cleaners: used to clean some single-ply roofing membranes prior to splicing, typically including heptane, hexane, white gasoline, and unleaded gasoline.

Solvent Welding: a process where a liquid solvent is used to chemically weld or join together two or more layers of certain membrane materials (usually thermoplastic).

Spalling: a condition in which the outer layer or layers of masonry or concrete material begin to break off or flake away.

Special Steep Asphalt: Type IV Asphalt. (See Asphalt.)

Specification: a statement of requirements for a given job or project. Usually describes products, materials, and processes to be used. A specification may also contain terms of the contract.

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

Splash Block: a small masonry or polymeric block laid on the ground or lower roof below the opening of a downspout used to help prevent soil erosion and aggregate scour in front of the downspout.

Splice: bonding or joining of overlapping materials. (See Seam.)

Splice Plate: a metal plate placed underneath the joint between two pieces of metal.

Splice-Tape: cured or uncured synthetic rubber tape used for splicing membrane materials.

Split: a rupture (generally linear) or tear in a material or membrane resulting from tensile forces.

Split Sheet: see Nineteen-lnch Selvage.

Split Slab: a term used to describe two separate concrete slabs. The first is placed as a slab-on-grade or suspended slab, and covered with waterproofing and a drainage system. The second slab, also referred to as a topping slab, is then placed over the underlying slab and waterproofing.

Spot Mopping: see Mopping.

Sprayed Polyurethane Foam (SPF): a foamed plastic material, formed by spraying two components, PMDI ([A] component) and a resin ([B] component) to form a rigid, fully adhered, water-resistant, and insulating membrane.

Spread Coating: a manufacturing process in which membranes are formed using a liquid compound, prepared in mixers and then fed to individual coalers. The mixture is spread onto a supporting reinforcement base layer. After coating, the material passes through a channel causing it to change from a paste to a solid membrane, in sheet form.

Square: 100 square feet (9.29 m2) of roof area.

Square-Tab Shingles: shingles with tabs that are all the same size and exposure.

Stainless Steel: an alloy of steel that contains a high percentage of chromium. Also may contain nickel or copper. Generally, has very good resistance to corrosion.

Standing Seam: a metal roof system that consists of an overlapping or interlocking seam that occurs at an upturned rib. The standing seam may be made by turning up the edges of two adjacent metal panels and overlapping them, then folding or interlocking them in a variety of ways.

Starter Course: the first layer of roofing, applied along a line adjacent to the downslope perimeter of the roof area. With steep-slope watershedding roof coverings, the starter course is covered by the first course.

Starter Sheets: (1) felt, ply sheet, or membrane strips that are made or cut to widths narrower than the standard width of the roll, used to start the shingling pattern at an edge of the roof; (2) particular width sheets designed for perimeters in some mechanically attached and fully adhered single-ply systems.

Starter Strip: roll roofing or shingle strips applied along the downslope eave line, before application of the first course of roofing, intended to fill spaces between cutouts and joints of the first course.

Static Load: any load, as on a structure, that does not change in magnitude or position with time.

Steel Joist (open web steel joist): normally used as a horizontal supporting member between beams or other structural members, suitable for the support of some roof decks.

Steep Asphalt: Type lil Asphalt. (See Asphalt.)

Steep-Slope Roof: a roof of suitable slope to accept the application of water shedding roofing materials.

Steep-Slope Roofing: a category of roofing that includes water shedding types of roof coverings installed on slopes exceeding 3:12 or 25%.

Steeple: a tower or spire, usually located on a church.

Step Flashing: individual pieces of material used to flash walls, around chimneys, dormers, and such projections along the slope of a roof. Individual pieces are overlapped and stepped up the vertical surface.

Stiffener Rib: small intermediate bends in a metal pan used to strengthen the panel.

Strapping (felts): a method of installing roofing rolls or sheet good materials parallel with the slope of the roof.

Straw Nail: a long-shanked nail. Sometimes used for fastening over tile at hips and ridges.

Stress: the internal resistance of a material to a force, measured as a force per unit area.

Stress-Crack: external or internal cracks within a material caused by long-term stress. Environmental factors, such as contact with corrosive material, usually accelerate stress-cracking.

Strike-Through: a term used in the manufacture of fabric-reinforced polymeric sheeting to indicate that two layers of polymer have made bonding contact through the scrim or reinforcement.

Strip Mopping: see Mopping.

Strip Shingles: asphalt shingles that are manufactured in strips, approximately three times as lone as they are

Strippable Films: (for metal) added protection of plastic films sometimes applied to coated or finished metals after the coil coating process. Applied after prime and top coats to resist damage to the finish prior to and during shipping, fabrication, and installation.

Stripping or Strip-Flashing: membrane flashing strips used for sealing or flashing metal flashing flanges into the roof membrane.

Stripping In: application of membrane stripping ply or plies.

Structural Panel: a panel designed to be applied over open framing in which a structural deck is not required.

Styrene Butadiene Rubber: high molecular weight polymers having rubber-like properties, formed by the random copolymerization of styrene and butadiene monomers.

Styrene Butadiene Styrene Copolymer (SBS): high molecular weight polymers that have both thermoses and thermoplastic properties, formed by the block copolymerization of styrene and butadiene monomers. These polymers are used as the modifying compound in SBS polymer modified asphalt roofing membranes to impart rubber-like qualities to the asphalt.

Substrate: the surface upon which the roofing or waterproofing membrane is applied (e.g., in roofing, the structural deck or insulation).

Sump: an intentional depression around a roof drain or scupper that serves to promote drainage.

Superimposed Loads: loads that are added to existing loads. For example, a large stack of insulation boards placed on top of a structural steel deck.

Surface Conductance: a unit of heat flow or heat exchange between a material and the air around it. Ventilation over a surface will decrease the thickness of the air film and reduce the thermal effect (increase the heat flow).

Surface Cure: curing or vulcanization that occurs in a thin layer on the surface of a manufactured polymeric sheet or other items.

Surface Dryness: surface dryness can be evaluated qualitatively by taping an 18 inch by 18 inch (0.46 m by 0.46 m) clear 4 mil polyethylene sheet to a concrete surface, and observing the moisture that may collect on the underside of the polyethylene sheet. Additional details of this procedure may be found in ASTM D 4263.

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 surface texture, orange peel surface texture, coarse orange peel surface texture, verge of popcorn texture, popcorn surface texture, treebark surface texture, and oversprayed surface texture.

Surfacing: the top layer or 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 SPF formulations to aid in mixing and controlling cell size.

Synthetic Rubber: any of several elastic substances resembling natural rubber, prepared by the polymerization of butadiene, isoprene, and other unsaturated hydrocarbons. Synthetic rubber is widely used in the fabrication of single-ply roofing membranes.