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This glossary was designed to help those not directly involved in roofing with their understanding of roofing terminology. Many technical and chemical terms were not included.

Tab: The portion of an asphalt shingle that is outlined by the cutouts.

Tapered Edge Strip: Tapered insulation strip used to ease transitions from one substrate elevation to another and to provide slope along roof perimeters.

Tape: See Joint Tape and Splice Tape.

Tar (ASTM DEFINITION): A brown or black bituminous material, liquid or semi-solid in consistency, in which the predominating constituents are bitumens obtained as condensates in the processing of coal, petroleum, oil-shale, wood, or other organic materials.

Tar Boil: A small bubble found in the flood coat of an aggregate-surfaced built-up roof; usually the result of trapped moisture vapor. Tar Boils are also known as blueberries or blackberries.

Tear-Off: To remove a roof system down to the structural substrate.

Tear Resistance: A material’s ability to withstand tearing. The test is performed by placing stress on an area of the material where a flaw is located. Tear Resistance is expressed in psi per inch width or kilonewton per meter width.

Tear Strength: The strength necessary to tear a material.

Tensile Strength: The amount of longitudinal pulling stress that a material can withstand before being pulled apart.

Termination: The sealed edges of a roof membrane.

Termination Bar (Term.’ Bar): A bar, usually metal or vinyl, used to seal and anchor the free edges of a roof membrane.

Terne: Sheet iron or steel plated with an alloy of three or four parts of lead to one part of tin, used as a roofing material.

Terra Cotta: A semifired ceramic clay used in building construction.

Thatch Roof: A roof covering made with straw, palms, reeds or other natural growths that are bound together in order to shed water.

Thermal Barrier: Material used in conjunction with polyurethane foam that is designed to inhibit the rise in temperature of the foam during a fire in order to delay the foam’s involvement in the fire. Time ratings for thermal barriers should exceed 15 minutes.

Thermal Conductance (C): A constant, equal to a material’s k-value (Thermal Conductivity) divided by the material’s thickness in inches; used often for materials of composite construction such as insulation. For more information, click here.

Thermal Conductivity (k): The heat energy that will be transmitted by conduction through 1 square foot of 1inch thick homogeneous material in 1 hour when there is a difference of 1 degree Fahrenheit perpendicularly across the two surfaces of the material. The higher the k-value, the lower the R-value. Materials with high k-values are good heat conductors, and conversely. For more information, click here.

Thermal Insulation: A material used to reduce heat flow.

Thermal Movement: Movement of a material resulting from temperature changes.

Thermal Resistance (R): The measure of a material’s ability to resist heat flow. The formula for Thermal Resistance is R = L / k where (L) is the material’s thickness and (k) is the material’s Thermal Conductivity constant. The higher a material’s R-value, the better it insulates, and conversely. For more information, click here.

Thermal Shock: The damage to a roof resulting from expansion and contraction which are the result of sudden extreme temperature changes. Thermal Shock often occurs when a cold rain shower suddenly cools a roof during a hot day.

Thermal Stress: Stress to a roof system or component caused by expansion and / or contraction from temperature change.

Thermoplastic: (1) adjective Becoming soft when heated and hard when cooled. (2)noun A thermoplastic resin, such as polystyrene or polyethylene.

Thermoset: A material that cannot be reshaped or formed by heating. EPDM and Butyl are thermosets.

Thinners: Liquids that are used to reduce a material’s viscosity when mixed but that evaporates during cure.

Thixotropy: Property of certain materials which liquefy when they are subjected to vibratory forces such as simple stirring or shaking and then solidify when left standing.

Throat: (1) The cutout of a shingle. (2) The narrowing passage located between a fireplace and smoke chamber or flue.

Through-Wall Flashing: A material that extends through a wall and is used to direct water entering a wall cavity to the exterior of the structure.

Tie-In: The joining of two different roof systems.

Tie-Off: A watertight seal used to terminate roof membranes at system adjuncts, terminations, flashings, or substrates. Can be temporary (see Night Seal) or permanent.

TIMA: Thermal Insulation Manufacturers Association

Toggle Bolt: A bolt with a separate toggle end that can be flattened to fit through a pre-drilled hole and that springs outward to provide securement when the bolt is tightened.

Tongue and Groove: Premanufactured materials with a convex "tongue" on one side and a concave "groove" on the other so that pieces of material can be joined together by placing the tongue of one piece into the groove of an adjacent piece so that the pieces fit more securely together.

Torque: Force applied to an object, particularly, to screw a mechanical fastener into a roof deck or substrate.

TPA: Tri-Polymer Alloy.

Traffic: Any rooftop activity that can potentially damage the roof surface.

Transverse Seam: The joint between the top of one metal roof panel and the bottom of the next panel, which runs perpendicular to the roof slope.

Treebark Surface Texture: An SPF surface deemed unacceptable for coating. This surface texture has deep valleys and is similar in appearance to rough tree bark.

Tuck Pointing: To remove old and deteriorated mortar from between masonry blocks and replace it with new mortar.


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