Tab: the exposed portion of strip shingles defined by cutouts.

 

Talc: whitish powder applied at the factory to the surface of some roofing materials (e.g., vulcanized EPDM membranes), used as a release agent to prevent adhesion of the membrane to itself.

 

Tapered Edge Strip: a tapered insulation strip used to (1) elevate and slope the roof at the perimeter and at curbs, and (2) provide a gradual transition from one layer of insulation to another.

 

Taping: the technique of using self-adhering tape-like materials to seam or splice single-ply membranes.

 

Tar: 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 Boils: bubbles of moisture vapor encased in a thin film of bitumen, also known as “blackberries.”

 

Tarred Felt: see Coal Tar Felt.

 

Tear-Off and Reroof: the removal of all roof system components down to the structural deck, followed by installation of a completely new roof system.

 

Termination: the treatment or method of anchoring and/or sealing the free edges of the membrane in a roofing or waterproofing system.

 

Terne: an alloy of lead and tin, used to coat sheets of carbon steel or stainless steel for use as metal roofing sheet.

 

Terra Cotta: low-fired clay, either glazed or unglazed.

 

Test Cut: a sample of the roof, which may contain all components or just the membrane, usually used to diagnose the condition of the existing membrane, evaluate the type and number of plies or number of membranes, or rates of application such as determine the weight of the average interply bitumen moppings.

 

Thermal Insulation: a material applied to reduce the flow of heat.

 

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: materials that soften when heated and harden when cooled. This process can be repeated provided that the material is not heated above the point at which decomposition occurs.

 

Thermoplastic Olefin Membrane (TPO): a blend of polypropylene and ethylene-propylene polymers. Colorant, flame retardants, UV absorbers, and other proprietary substances which may be blended with the TPO to achieve the desired physical properties. The membrane may or may not be reinforced.

 

Thermoset: a material that solidifies or “sets” irreversibly when heated. This property is usually associated with cross-linking of the molecules induced by heat or radiation.

 

Through-Wall Flashing: a water-resistant material, which may be metal or membrane, extending through a wall and its cavities, positioned to direct water entering the top of the wall or cavity to the exterior, usually through weep holes.

 

Tie-Off: (in roofing and waterproofing) the transitional seal used to terminate a roofing or waterproofing application at the top or bottom of flashings, or by forming a watertight seal with the substrate, membrane or adjacent roofing or waterproofing system.

 

Toggle Bolt: a two-piece assembly consisting of a threaded bolt and an expanding clip that can fit through a drilled hole. The clip can spring outward to provide anchorage from the blind side.

 

TPO: Thermoplastic Olefin.

 

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