Dampproofing: treatment of a surface or structure to resist the passage of water in the absence of hydro-static pressure..

Dead Level: essentially horizontal or flat, as in a roof deck or rooftop with no intentional slope to the roof drains. Also referred to as zero (0) slope. (See Slope.).

Dead Loads: permanent non-moving loads that result from the weight of a building's structural and architectural components, mechanical and electrical equipment, and the roof assembly itself. Essentially the same as "dead weight" or "dead weight loads.".

Deck: a structural component of the roof of a building. The deck must be capable of safely supporting the design dead and live loads, including the weight of the roof systems, and the additional live loads required by the governing building codes. Decks are either non-combustible (e.g., corrugated metal, concrete, or gypsum) or combustible (e.g., wood plank or plywood), and provide the substrate to which the roofing or waterproofing system is applied..

Deflection (Bowing, Sagging): the downward displacement of a structural member or system under load.

Degradation: a deleterious change in the chemical structure, physical properties, or appearance of a material due to natural or artificial exposure (e.g., exposure to radiation, moisture, heat, freezing, wind, ozone, oxygen, etc.).

Delamination: separation of the laminated layers of a component or system..).

Design Loads: those loads specified in building codes or standards published by federal, state, county, or city agencies, or in owners' specifications to be used in the design of a building..).

Dew Point Temperature: the temperature at which water vapor condenses in cooling air at the existing atmospheric pressure and vapor content. Cooling at or below the dew point will cause condensation.

Dimensional Stability: the ability of a material to resist change in length, width, and/or thickness that results from exposure to elevated or freezing temperatures, and moisture, over time.

Downspout: a conduit used to carry runoff water from a scupper, conductor head, or gutter of a building to a lower roof level, or to the ground or storm water runoff system..).

Drain: an outlet or other device used to collect and direct the flow of runoff water from a roof area..).

Drip Edge: a metal flashing, or other overhanging component, with an outward projecting lower edge, intend-ed to control the direction of dripping water and help protect underlying building components. A drip edge also can be used to break the continuity of contact between the roof perimeter and wall components to help prevent capillary action..).

Dynamic Load: any load which is nonstatic, such as a wind load or a moving live load.

Eave Height: the vertical dimension from finished grade to the eave.

ECH: polyepichlorohydrin, commonly referred to as epichlorohydrin. (See Epichlorohydrin.)

Edge Stripping: membrane flashing strips cut to specific widths used to seal/flash perimeter edge metal and the roof membrane.

Edge Venting: the practice of providing regularly spaced or continuously protected (e.g., louvered) openings along a roof edge or perimeter, used as part of a ventilation system to dissipate heat and moisture vapor.

Efflorescence: the formulation of crystalline deposits, generally whitish in color, on the surface of stone, brick, concrete, or other masonry surface when moisture moves through and evaporates on the masonry. May also be caused by free alkalies leached from mortar, grout, or adjacent concrete.

Elasticity: the property of matter by virtue of which it tends to return to its original size and shape after removal of a stress or force which caused a deformation.

Elastomer: natural or synthetic material which, at room temperature, can be stretched under low stress and, upon immediate release of the stress or force, will return quickly to its approximate original dimensions.

Elastomeric: the elastic, rubber-like properties of a material that will stretch when pulled and will return relatively quickly to its original shape when released.

Elastomeric Coating: a coating system which, when fully cured, is capable of being stretched at least twice its original length (100% elongation) and recovering to its original dimensions.

Elongation: the ability of a material (e.g., roofing membrane) to be stretched by the application of a force.

Embedment: (1) the process of installing or pressing-in a reinforcement felt, fabric, mat or panel uniformly into bitumen or adhesive; (2) the process of pressing granules into coating during the manufacture of factory-pre-pared roofing; (3) the process whereby ply sheet, aggregate, or other roofing components settle into hot- or cold-applied bitumen via the force of gravity.

Embrittlement: the loss of flexibility or elasticity of a material. The transition of a flexible material to a brittle state.

Emulsion: a dispersion of fine particles or globules in a liquid. (See Asphalt Emulsion and Bitumen Emulsion.)

End Lap: the distance of overlap where one ply, panel, or piece extends beyond the end of the immediately adjacent underlying ply, panel, or piece.

Envelope (Bitumen-Stop): a continuous edge seal formed at the perimeter and at penetrations by extending the base sheet or one ply of felt beyond the edge of the membrane field plies. After all overlying field plies or insulation are in place, the extended ply is turned back onto the membrane and adhered. The envelope is intended to prevent bitumen seepage from the edge of the membrane.

EPDM: Ethylene Propylene Diene Monomer (See also Ethylene Propylene Diene Terpolymer.)

Epichlorohydrin (ECH): a synthetic rubber including two epichlorohydrin based elastomers. It is similar to and compatible with EPDM. ECH is typically used in lieu of EPDM when enhanced resistance to animal fat or other oils is needed.

Epoxy: a class of synthetic, thermosetting resins that produce tough, hard, chemical-resistant coatings and adhesives.

Equilibrium Moisture Content (EMC): (1) the moisture content of a material stabilized at a given temperature and relative humidity, expressed as percent moisture by weight; (2) the typical moisture content of a material in any given geographical area.

Equiviscous Temperature (EVT): the temperature at which a bitumen attains the proper viscosity for built-up membrane application.

Equiviscous Temperature (EVT) Application Range: the recommended bitumen application temperature range. The range is approximately 25°F (14°C) above or below the EVT, thus giving a range of approximately 50°F (28°C). The EVT Range Temperature is measured in the mop cart or mechanical spreader just prior to application of the bitumen to the substrate.

Equiviscous Temperature (EVT) for Asphalt: the recommended EVT for roofing asphalt (ASTM D312, Type I, II, III, or IV) is as follows:

Mop Application: the temperature at which the asphalt's apparent viscosity is 125 centipoise (0.125 Pa.s).
Mechanical Spreader Application: the temperature at which the asphalt's apparent viscosity is 75 centipoise (0.075 Pa.s).
Note: If there are simultaneous mop and mechanical spreader applications, in order to avoid the use of two kettles, the EVT for mechanical spreader application may be used for both application techniques.

Equiviscous Temperature (EVT) for Coal Tar: the recommended EVT for roofing coal tar (ASTM D 450, Type I or III) is the temperature at which the coal tar's apparent viscosity is 25 centipoise (0.025 Pas).

Ethylene Interpolymers (EIP): a group of thermoplastic compounds generally based on PVC polymers from which certain single-ply roofing membranes can be formulated.

Ethylene Propylene Diene Terpolymer (EPDM): designated nomenclature of ASTM for a terpolymer of ethylene, propylene, and a diene. EPDM material is a thermosetting synthetic elastomer.

EVT: Equiviscous Temperature

Exhaust Ventilation: air that is typically vented or exhausted from the roof cavity, typically through vents installed on the upslope portion of the roof. For example, with most steep-slope roof assemblies exhaust vents are typically located at or near the ridge.

Exotherm: heat generated by a chemical reaction.

Expansion Cleat: a cleat designed to handle thermal movement of the metal roof panels.

Expansion Joint: a structural separation between two building elements that allows free movement between the elements without damage to the roofing or waterproofing system.