Glossary of Roofing and Waterproofing Terms

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Tab: the exposed portion of strip shingles defined by cutouts. (See Figure 25.)

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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: (1) the technique of connecting joints between insulation boards or deck panels with tape; (2) 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.

Tear Resistance: the load required to tear a material, when the stress is concentrated on a small area of the material by the introduction of a prescribed flaw or notch. Expressed in psi (pounds force) per inch width or kN/m (kilonewton per meter width).

Tear Strength: the maximum force required to tear a specimen.

Tensile Fatigue Resistance: the ability of a given membrane material to resist "fatigue" and/or other damage (such as loss of elasticity) caused by the alternate stretching and relaxing of the material over a period of time.

Tensile Strength: the maximum force (longitudinal pulling stress) a material can bear without tearing or breaking apart.

Tensile Test: a test in which a specimen is subjected to increasing longitudinal pulling stress until fracture occurs.

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 mappings.

Thatch Roof: the covering of a roof usually made of straw, reed, or natural foliage (palms) bound together to shed water.

Therm: a unit of heat equivalent to 100,000 BTUs (105.6-106). Commonly used by utilities in quoting prices or costs.

Thermal Barrier: a material applied over polyurethane foam designed to slow the temperature rise of the foam during a fire and delay its involvement in the fire. Thermal barriers for use with SPF must have a time rating of not less than 15 minutes.

Thermal Block: a compression-resistant insulation block installed between the structural steel and the panel to maintain insulation value.

Thermal Conductance (C): a unit of heat flow that is used for specific thicknesses of material or for materials of combination or composite construction, such as laminated insulation. The formula for thermal conductance is:

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Thermal Conductivity (k): the heat energy that will be transmitted by conduction through 1 square foot of 1 inch thick homogeneous material in one hour when there is a difference of 1 degree Fahrenheit perpendicularly across the two surfaces of the material. The formula for thermal conductivity is: k = Btu/Square FooVlnch /Hour/Degree Fahrenheit

Thermal Image: a visual representation of temperature distribution over a surface area. The image is displayed on a screen, presenting the response to infrared light waves.

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 Resistance (R): an index of a material's resistance to heat flow; it is the reciprocal of thermal conductivity (k) or thermal conductance (C). The formula for thermal resistance is:

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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.

Thermogram: a visible light record of the display of an infrared camera system via a Polaroid print, 35mm film, video tape, or computer generated image.

Thermography: a technique for producing heat "pictures" from the radiant energy emitted from stationary or moving objects without in any way influencing the temperatures of the objects under view. The electronic generation and display of a visible image of an infrared spectrum.

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.

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

Thixotropic: having the property of decreasing viscosity with increasing shear stress. A coating is thixotropic if it thins with stirring or pumping but thickens when movement ceases.

Thread Count: the number of threads per inch in each direction, with the warp mentioned first, and the fill second, (e.g., a thread count of 20 x 10 means 20 threads per inch [25.4mm] in the warp and 10 threads per inch [25.4mm] in the fill direction).

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.

TIMA: Thermal Insulation Manufacturers Association

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.

Tongue and Groove Planks: one of the oldest types of dimensional structural wood used as roof decking. The sides are cut with convex and concave grooves so adjacent planks may join in alignment with each other to form a uniform roof deck.

TPA: Tri-Polymer Alloy.

TPO: Thermoplastic Olefin.

Traffic Bearing: in waterproofing, a membrane formulated to withstand a predetermined amount of pedestrian or vehicular use with separate protection and a wear course.

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: the surface shows a coarse texture where valleys from sharp angles. This surface is unacceptable for proper coating and protection.

Tuckpointing: the process of removing deteriorated mortar from an existing masonry joint and troweling new mortar or other filler into the joint.

Two-Part System: a coating of SPF formed by the mixing and (usually) the reaction of two different materials.


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