| Term | Definition |
| Quad | 1. A unit of energy equal to one quadrillion (1,000,000,000,000,000) BTUs. 2. Quadrangle. 3. Quadriphonic. |
| Quadrangle | 1. A four sided enclosure surrounded by buildings. 2. A quadrilateral. 3. One of the survey map sheets published by the USGS. |
| Quadrant | 1. A quarter of a circle. 2. An instrument for measuring altitudes. 3. A hardware device to fasten together the upper and lower leaves of a Dutch door. |
| Quadrel | A square tile; a quarrel. |
| Quadrilateral | A polygon of four sides. |
| Quadripartite | Having four parts; quadripartite vaulting is the commonest form of groined and also of ribbed vaulting. |
| Quadriphonic | Sound recorded or transmitted utilizing four transmission channels. |
| Quadrisect | To divide into 4, usually equal, parts |
| Quadruplex Cable | Four wire cable. |
| Quag | A marsh. |
| Quagmire | A soft boggy or marshy area that gives way under foot. |
| Quake | An earthquake. |
| Qualified Historical Building (Or Structure) | Any structure or collection of structures deemed important to the history, architecture or culture of an area by an appropriate local or state governmental jurisdiction. This shall include structures of national, state or local historical registers or off |
| Quality | The degree of excellence of a thing. |
| Quality Control | All the activities undertaken to ensure adequate quality in manufactured products and in on-site construction. |
| Quantity | The size, extent, weight, amount, number, or volume of a thing. |
| Quantity Survey | Detailed listing of all materials, equipment, and services needed to complete a project. |
| Quantity Surveyor | A person who measures and prices building work; see Quantity Survey. |
| Quantum | A desired or allowed amount. |
| Quarrel | 1. A square or lozenge-shaped piece of material, especially a piece of glass, set diagonally, as in a latticed sash; also called a quarrel pane. 2. The opening in a sash prepared for such glazing. |
| Quarry | An open excavation for removing building stone, slate, or limestone; a rock pit. |
| Quarry Bed | The side of a piece of building stone that is parallel with the natural strata or veins. |
| Quarry Tile | A large, fired, clay floor tile, usually unglazed. |
| Quarry tile | A man-made or machine-made clay tile used to finish a floor or wall. Generally 6" X 6" X 1/4" thick . |
| Quarry-Faced | Stone having a rough face as if just split from the quarry. |
| Quarter Bend | A drainage pipe fitting which makes a 90 degree angle. |
| Quarter Drop Match | See Set Match. |
| Quarter Hollow | A concave molding or cavetto of which the transverse section is an arc of about 90 degrees, the converse of a quarter round, or ovolo. |
| Quarter round | A small trim molding that has the cross section of a quarter circle. |
| Quarter Round | Wood molding with a cross section in the shape of a quarter circle. |
| Quarter Width | The unit of yard measure (1/4) used in referring to carpet or loom widths; early European carpet was woven in widths of 27 inches or 3/4 yards; hence, 4/4 = 1-yard width or 3'; 12/4 width = 9' and 16/4 width = 12'. |
| Quartersawed Lumber | Edge-grained lumber. |
| Quartz | Crystalline silica; a hard brittle mineral breaking with a glasslike fracture, and usually transparent to translucent, and colorless, or of a white, pink, and amethystine hue. |
| Quartzite | A strong sandstone cemented by quartz, about 98 percent silica. |
| Quasi Contract | Application of contract rules of law to parties that do not have a contractual relationship. |
| Quatrefoil | A four cusped circular element in Gothic tracery. |
| Quay | A structure built along the bank of a waterway for use as a landing place. |
| Queen | 1. A half brick made by cutting a whole brick in two lengthwise as for a corner in a soldier course. 2. A half brick used to prevent vertical joints falling above one another. |
| Queen Anne | The architecture and furniture style of England, under Dutch influence, during the short reign of Anne, 1702-1714. |
| Queen Closer | A brick cut in half lengthwise. |
| Queen Truss | A truss framed with queen posts. |
| Quenching | 1. Cooling of steel in cold water to increase its hardness. 2. Rapid cooling of metal in a heat treating process. |
| Quick Assets | 1. Assets easily converted to cash. 2. Current assets without inventory. |
| Quick Burst | The inter-pressure required to burst a pipe or fitting due to an internal pressure build-up, usually within 60 to 90 seconds. |
| Quick Drying | A material with a relatively short drying time. |
| Quick Fix | An expedient often inadequate solution to a problem; a Band-Aid Approach. |
| Quick Set | 1. See Flash Set. 2. In gypsum wallboard joints, a joint compound that chemically hydrates prior to drying; also called Fast Set. |
| Quick-Connect Coupling | A device which permits easy and fast connecting of two fluid lines. |
| Quicklime | The first solid product CaO that is obtained by calcining limestone and that develops great heat and becomes crumbly when treated with water; lime; before it can be used in construction, quicklime must be slaked in water and aged for at least 2 weeks. |
| Quicksand | 1. Fine sand or silt that is prevented from settling firmly together by upward movement of ground water. 2. Any wet inorganic soil so unsubstantial that it will not support any load. |
| Quicksilver | Mercury. |
| Quiet Title Action | A lawsuit brought to remove a claim on the title of real property. |
| Quincunx | An arrangement of five objects in which four are at the corners and one is at the center at the crossed diagonals, in the manner of a dice or a five playing card, used in planting trees. |
| Quintefoil | A five cusped element in Gothic tracery. |
| Quirk | A groove separating two parts of a molding. |
| Quitclaim Deed | A form of deed in the nature of a release containing both words of grant and of release; it does not provide a guarantee or warranty of title. |
| Quoin | Cornerstones forming the external angle of a building; bricks or block masonry that project out from the walls at the corners of a building for ornamental effect. |
| Quonset | A prefabricated metal building with a semicylindrical corrugated roof. |