Dado - A rectangular groove across the width of a board or plank. In interior decoration, a special type of wall treatment.

Decay - Disintegration of wood or other substance through the action of fungi.

Density - The mass of substance in a unit volume. When expressed in the metric system, it is numerically equal to the specific gravity of the same substance.

Dewpoint - Temperature at which a vapor begins to deposit as a liquid. Applies especially to water in the atmosphere. Dimension. See Lumber dimension.

Direct Nailing - To nail perpendicular to the initial surface or to the junction of the pieces joined. Also termed face nailing.

Doorjamb, Interior - The surrounding case into which and out of which a door closes and opens. It consists of two upright pieces, called side jambs, and a horizontal head jamb.

Dormer - An opening in a sloping roof, the framing of which projects out to form a vertical wall suitable for windows or other openings.

Downspout - A pipe, usually of metal, for carrying rainwater from roof gutters.

Dressed and Matched (tongued and grooved) - Boards or planks machined in such a matter that there is a groove on one edge and a corresponding tongue on the other.

Drier Paint - Usually oil-soluble soaps of such metals as lead manganese, or cobalt, which, in small proportions, hasten the oxidation and hardening (drying) of the drying oils in paints.

Drip - (a) A member of a cornice or other horizontal exterior finish course that has a projection beyond the other parts for throwing off water. (b) A groove in the under, side of a sill or drip cap to cause water to drop off on the outer edge instead of drawing back and running down the face of the building.

Drip Cap - A molding placed on the exterior top side of a door or window frame to cause water to drip beyond the outside of the frame.

Drywall - Interior covering material, such as gypsum board or plywood, which is applied in large sheets or panels.

Ducts - In a building, usually round or rectangular metal pipes for distributing warm air from the heating plant to rooms, or air from a conditioning device or as cold air returns. Ducts are also made of asbestos and composition materials.