T | Roofing Glossary

Roofing Glossary, a collection of terms used in the roofing industry

There are 639 entries in this glossary.

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Term	Definition
T-joint	the condition created by the overlapping intersection of three or four sheets in the membrane.
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	(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.”
Tear Strength	the maximum force required to tear a specimen.
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).
Tensile Strenght	the strength of a material under tension as distinct from torsion, compression or shear.
Tension Leveling	the process of pulling metal coil stock between two spools under a certain pressure to help reduce side camber and potential oil canning in the coil stock caused by manufacturing and cutting processes.
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 system or assembly which exposes the roof deck and is used to diagnose the condition of the membrane, evaluate the type and number of plies or number of membranes, or rates of application (e.g., the weight of the average interply bitumen moppings).
Thermal Block	a compression-resistant insulation block installed between structural steel roof panels and their supporting members to help maintain insulation R-values and reduce condensation.
Thermal Bridge	the penetration of a material of high thermal conductivity (e.g., a metal insulation or roof membrane fastener) through a material of low thermal conductivity (e.g., thermal insulation); the result is a lowered thermal resistance for the assembly. The NRCA Roofing and Waterproofing Manual—Fifth Edition Glossary 1005
Thermal Conductance	the time rate of heat flow through a unit area of a body induced by a unit temperature difference between bodies. In English (inch-pound) units of measurement, the number of BTUs that pass through a specified thickness of a one square foot (0.09 m2) sample of material in one hour with a temperature difference between the two surfaces of 1° F. In English (inch-pound) units it is expressed as Btu/h•ft2•F. Note 1: A thermal conductance (C) value applies to a specific thickness of a specific material. Note 2: It is mathematically incorrect to multiply or divide the thermal conductance (C) value for a specific thickness of a material to determine the thermal conductance value of a different thickness of the same material. Note 3: It is mathematically incorrect to add thermal conductance (C) values to determine overall thermal performance. If it is necessary to determine the overall thermal performance of a construction, it is appropriate to convert the individual thermal conductance (C) values to thermal resistance (R) values (i.e., R= 1/c), and then add the thermal resistance values (i.e., RT=R1, + R2 + ...). Aliases (separate with \|): C
Thermal Conductivity	the time rate of heat flow through a unit area of a homogeneous material in a direction perpendicular to isothermal planes induced by a unit temperature gradient is called thermal conductivity (k or kvalue). In English (inch-pound) units of measurement, it is the number of BTUs that pass through a 1 inch (25 mm) thickness of a 1 square foot (0.09 m2) sample of material in one hour with a temperature difference between the two surfaces of 1°F. In English (inch-pound) units it is expressed as Btu•inch/h•ft2•°F. Note 1: A thermal conductivity (k) value applies to 1 inch (25 mm) thickness of a specific material. Note 2: It is mathematically incorrect to add, multiply, or divide the thermal conductivity (k) value of a material to determine the thermal performance value of a different thickness of the same material. If it is necessary to determine the thermal performance of a specific thickness of a material, it is appropriate to convert the thermal conductivity (k) of the material to a thermal resistance (R) value (i.e., R = 1/k), and then perform the mathematical calculation. Aliases (separate with \|): K
Thermal Cycling	sequence of values caused by a repetitive temperature differential due to changes in radiant energy.
Thermal Expansion	the increase in the dimension or volume of a body due to temperature variations.
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	under steady conditions, thermal resistance is the mean temperature difference between two defined surfaces of material or construction that induces unit heat flow through a unit area. In English (inch•pound) units it is expressed as °F•ft2•h/Btu. Note 1: A thermal resistance (R) value applies to a specific thickness of a material or construction. Note 2: The thermal resistance (R) of a material is the reciprocal of the thermal conductance (C) of the same material (i.e., R = 1/C). Note 3: Thermal resistance (R) values can be added, subtracted, multiplied, and divided by mathematically appropriate methods.
Thermal Shock	the stress-producing phenomenon resulting from sudden temperature changes in a roof membrane when, for example, a cold rain shower follows brilliant sunshine.
Thermal Stress	stress introduced by uniform or non-uniform temperature change in a structure or material that is contained against expansion or contraction. The NRCA Roofing and Waterproofing Manual—Fifth Edition 1006 Glossary