Damp Proof Course – A non-permeable membrane placed above ground level in a brick or stonewall to prevent moisture seeping up into the structure.

Damp Proofing – Actions taken to stop the passage of moisture through a wall or floor. Material i.e.; plastic sheeting used to stop moisture penetration.

Decking – Wood covering the roof, under the shingles. Usually OSB board.

Deferred Maintenance – Maintenance that has not been carried out when it was needed.

Deflection – Bending or sagging that occurs when structures are subjected to heavy weights, furnishings, people, Etc. Some sagging is acceptable.

Deterioration – Damage occurring over a period of time, due to a lack of maintenance.

Door Jam – The frame that holds a door. The wood on both sides are called the jambs, an across the top the head jam.

Dormer – Framed window unit projecting through the sloping side of the roof.

Double Coverage – Application of asphalt roofing such that the lapped portion is at least two inches wider than the exposed portion, resulting in two layers of roofing material over the deck.

Double Hung Window – Window with two moving sashes one above the other.

Double-glazing – Two panes of glass with an air space between them in a sealed unit. Increases the insulation factor. May be gas filled to further increase the insulation.

Doubled Up Conductors – The wiring of two or more circuits to a fuse/breaker.

Downspout – Pipe between the gutter and the drain.

Drip Edge – A non-corrosive, non-staining metal used along the eaves and rakes to allow water run-off to drip clear of underlying construction.

Dry Rot – A fungus that destroys wood, needs moisture and warmth in a dark environment.

Drywall – Usually refers to gypsum board, a board made of plaster sandwiched between two sheets of paper.

Ducts – The large pipes or tubes used to move air between the heating or cooling equipment and the vents.