dado: A rectangular groove across the width of a board or plank. In interior decoration, a special type of wall treatment.
damp-proofing: A process used on concrete, masonry and stone surfaces to repel water in order to prevent the coated surface from absorbing rainwater while still permitting moisture vapor to escape from the structure, as moisture vapor readily penetrates coatings of this type. The term damp-proofing generally applies to surfaces above grade, while the terms waterproofing generally applies to surfaces below grade.
damper: An air valve that regulates the flow of air inside the flue of a furnace or fireplace.
darby: A flat tool used to smooth concrete flatwork immediately after screeding. Also called a bullfloat.
dead load: The static design-weight of a roof and any permanent fixtures attached above or below it.
decay: Disintegration or rot of wood or other substance through the action of mold.
deck: An elevated platform typically located outdoors at a residential structure. The term deck is also commonly used to refer to the above-ground floors in a multi-level parking garage.
deck paint: An enamel paint with a high degree of resistance to mechanical wear designed for use on such surfaces as porch floors.
decorative: Ornamental; not required for the operation of essential systems or components of a home or building.
deem: to form or have an opinion; to consider as; to judge; to conclude; to regard or consider in a specified way.
defensible space: An area around a structure that is cleared of trees, brush, and other potential fuel whose purpose is to slow the rate of an advancing wildfire.
deferred-maintenance items: Deficient items that cannot be remedied with routine maintenance, generally caused by neglect.
deflect: To bend or deform under weight.
deflection: The amount of bending movement of any part of a structural member perpendicular to the axis of the member under an applied load.
dehumidistat: A control mechanism used to operate a mechanical ventilation system based on the relative humidity in the home.
density: The mass of substance in a unit volume. When expressed using the metric system, it is numerically equal to the specific gravity of the same substance.
describe: To report in writing on a system or component by its type or other observed characteristics in order to distinguish it from other components used for the same purpose.
design pressure: Specified pressure that a product or component is designed to withstand.
designer: One who designs houses, interiors, landscaping or other objects. When used in the context of residential construction, it usually suggests that a designer is not a licensed architect. Most jurisdictions don't require an architectural license for most single-family construction.
destructive: An act of demolishing, damaging or probing any system, structure or component, or to dismantle any system or component that would not be taken apart by an ordinary person in the course of normal maintenance.
determine: To arrive at an opinion or conclusion pursuant to examination.
dew point: The temperature at which vapor condenses from the atmosphere and forms water.
dimensional lumber: Yard lumber from 2 inches up to, but not including, 5 inches thick and 2 or more inches wide, and includes joists, rafters, studs, planks and small timbers.
direct nailing: To nail perpendicular to the main surface or the junction of the pieces joined. Also called face-nailing.
direct-gain system: A passive solar heating system in which sunlight penetrates and directly warms the house's interior.
disconnected: Shut down.
dismantle: To open, take apart or remove any component, device or piece that would not typically be opened, taken apart or removed by an occupant.
disposer: A device that grinds food sufficiently to enter drains for disposal without clogging them.
distortion: Alteration of viewed images caused by variations in glass flatness or in homogeneous portions within the glass; an inherent characteristic of heat-treated glass.
diverter: A valve that has a single inlet and directs water to one of two outlets. Diverters are used with hand-held showers, shower risers, tub-and-shower combinations, and kitchen faucet sprayers.
diverter valve: A device that changes the direction of water flow from one faucet to another.
Dolly Varden siding: Beveled wood siding that is rabbeted on the bottom edge.
door jamb (interior): The surrounding case into and out of which a door closes and opens, consisting of two upright pieces, called side jambs, and a horizontal head jamb.
dormer: A converted attic with windows projecting through a sloping roof.
double coverage: The application of asphalt roofing so that the lapped portion is at least 2 inches wider than the exposed portion, resulting in two layers of roofing material over the roof deck.
double glazing: Two lites of glass in a window that are separated by an air space within an opening to improve insulation against heat transfer and/or sound transmission. In insulated glass units (IGUs), the air between the glass sheets is thoroughly dried and the space is sealed, eliminating the potential for condensation and providing superior insulating properties.
double plate: Two layers of 2x4s that are placed on top of the studs in a wall framing.
double tree: Refers to a precast roof deck panel poured with two fins in its underside to impart flexural rigidity.
double-hung window: A window with sashes that slide vertically and allow opening from the top and bottom.
double-strength glass: Float glass that is approximately 1/8-inch thick.
downspout: The pipe that carries water down from the gutter or scupper. Also called a leader.
draw: The amount of progress billings/payments that are available to a contractor under a construction contract with a fixed payment schedule.
drawing detail: A top-view scale drawing of a building or roof showing the roof's perimeter and indicating the projections and roof-mounted equipment.
drawing outline: A top-view scale drawing of a building or roof showing only the perimeter.
dressed-and-matched (D&M): Boards or planks machined in such a manner that there is a groove on one edge and a corresponding tongue on the other. Also called tongue-and-groove (T&G).
dressed-size lumber: The dimension of lumber after shrinking from its green dimension and machining it to size or pattern.
drier paint: Oil-soluble soaps of lead manganese or cobalt that, in small proportions, hasten the oxidation and hardening (drying) of the drying oils in paints.
drip: A member of a cornice or other horizontal exterior finish course that has a projection beyond the other parts for the purpose of throwing off water. Also, a groove in the underside 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 a building.
drip cap: A molding placed on the exterior topside of a door or window frame to cause water to drip beyond the outside of the frame.
drip edge: A component designed to prevent water from running back or under an overhang.
drippage: Bitumen material that drips through roof deck joints or over the edge of a roof deck.
drop siding: Siding that is usually 3/4-inch thick and 6 or 8 inches wide with tongue-and-groove or shiplap edges, often used as siding without sheathing in secondary buildings.
dropping a stringer: In carpentry, this term refers to cutting short on the bottom of a stair to allow for thickness of the first tread.
dry glazing: A term used to describe various means of sealing monolithic and insulated glass in the supporting framing system with synthetic rubber and other elastomeric gasket materials. Also called compression glazing.
dry rot: See fungal wood rot.
dry seal: A weather seal between a window's glass and sash by use of strips or gaskets of neoprene, EPDM, silicone or other flexible material. A dry seal may not be completely watertight.
dry sheet: A ply that is mechanically attached to wood or gypsum decks to prevent asphalt or pitch from penetrating the deck and leaking into the building below.
dry-in: To make a building waterproof.
drywall: A gypsum-board material used for interior walls and ceilings.
drywall construction: A type of construction whereby the interior wall finish is applied in a dry condition, generally in the form of sheet materials or wood paneling, as opposed to plaster. The edges should be smooth and the corners rounded off.
drywall hammer: A special hammer with a convex round and checked head used for nailing up gypsum board. Also called an axe and a hatchet.
drywall nail: Nails used for hanging drywall (to be taped and finished later) that have adequate holding power and a head design that does not cut the face paper. They must also be of the proper depth to provide exactly 1 inch of penetration into the framing member. Nails commonly used are chemically-etched and are designed with a cupped head.
duct: A cylindrical or rectangular tube, usually constructed of sheet metal, used as an exhaust/intake channel to distribute warm air from a furnace or cooled air from an air conditioner, or as cold-air returns. The installation is referred to as ductwork.
ductwork: A system of distribution channels used to transmit heated or cooled air from a central HVAC system throughout a home.
due diligence: A level of care in the inspection process that varies, depending on the scope of work agreed to by the inspector and his/her client.
due-on-sale: A clause in a mortgage contract that requires the borrower to pay the entire outstanding balance upon sale or transfer of the property.
dumbwaiter: An elevator with a maximum footage of not more than 9 square feet, not more than 4 inches of headroom, and a maximum capacity of 500 pounds used for carrying materials only.
DuraBoard®, Durock®: A panel made of concrete and fiberglass and used as a ceramic tile backing material on bathtub decks. Also known as WonderBoard®.
durometer: A gauge used to measure the hardness of an elastomeric material.
dwelling unit: Sometimes used interchangeably with residential unit, a single unit of a multi-unit housing structure (of more than four individual units) that provides complete, independent living facilities, including permanent provisions for living, sleeping, eating, cooking and sanitation.
DWV (drain, waste & vent; drain-waste-vent): The pipes in a plumbing system that remove wastewater.