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

 

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-Level Asphalt: see Asphalt.

 

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.

 

Diffusion: the movement of water vapor from regions of high concentration (high water vapor pressure) toward regions of lower concentration (due to random thermal molecular motion).

 

Dimensional Shingle: a shingle that is textured, overlayed, or laminated and designed to produce a three-dimensional effect. (Also see Laminated Shingles and Architectural Shingles.)

 

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.

 

Dome: a roof that is shaped like a half-circle, or a variation of one.

 

Dormer: a framed projection through the sloping plane of a roof.

 

Double Lock Standing Seam: a standing seam that utilizes a double, overlapping interlock between two seam panels. (See Standing Seam.)

 

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, intended 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.

 

Dry-In or Dry-In Felt: usually the underlayment or the process of applying the underlayment for steep roofing.

 

top of page