Term | Definition |
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Damper | A movable vane used to vary the volume of air passing through a duct, inlet, or outlet. |
Damping Capacity | The ability of a material to absorb vibrational energy. |
Darby | A tool used to level concrete in a form after it has been screeded. |
Dead Load | Load on a building element contributed by the weight of the building materials. |
Decibel (dB) | A unit for measuring sound energy or power. Adopted for convenience in representing vastly different sound pressures. |
Deciduous | Describing trees that shed their leaves annually, as opposed to evergreen. |
Decoupling | Separation of elements to reduce or eliminate the transfer of sound, heat or physical loads from one element to the other. |
Deed | A written instrument that is used to transfer real property from one party to another. |
Deflection | Displacement that occurs when a load is applied to a member or assembly. The dead load of the member or assembly itself causes some deflection as may occur in roofs or floors at mid-span. Under applied wind loads maximum deflection occurs at mid-height in partitions and walls. |
Deflection Limitation | Maximum allowable deflection is dictated by the bending limit of the finish material under the required design load (e.g., usually 5 psf for interior partitions). |
Deformation | Change in shape of a body brought about by the application of a force internal or external. Internal forces may result from temperature, humidity or chemical changes. External forces from applied loads can also cause deformation. |
Degree Days | The number of degrees that the mean temperature for any day at a particular locatoin is below 65 degrees Fahrenheit. |
Dehumidification | The removal of water vapor from the air. |
Dehumidifier | A cooling, absorption, or adsorption device used for removing moisture from the air. |
Dehydration | The removal of water vapor from any substance. |
Delamination | The separation of the plies in a laminate or plies from a base material. |
Density | (1) With regards to materials, a measurement that compares the amount of matter an object has relative to its volume. (2) In city or site planning, a measure of the number of people, families, etc. that occupy a specified area. |
Desiccant | Any absorbent, adsorbent, liquid, or solid that removes water or water vapor from a material. |
Desiccation | The process of evaporating or removing water vapor from a material. |
Design Load | Combination of weight (dead load) and other applied forces (live loads) for which a building or part of a building is designed. Based on the worst possible combination of loads. |
Dew Point | The temperature at which air becomes saturated (100 percent relative humidity) with moisture and below which condensation occurs.
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Dewatering | Pumping subsurface water from an excavation to maintain dry and stable working conditions. |
Diaphragm | A horizontal roof or floor structural element designed to resist lateral loads and transmit them to shear walls (vertical resisting elements). |
Dielectric Strength | The maximum voltage a dielectric (nonconductor) can withstand without fracture. |
Diffuser | A circular, square, or rectangular air distributing outlet, usually in the ceiling, that has members to discharge supply air in several directions, mixing the supply air with the secondary air in the room. |
Dimensional Lumber | Lumber from 2 inches (50.8 mm) up to, but not including, 5 inches (127 mm) thick and 2 inches (50.8 mm) or greater in width. |
Direct Current (DC) | Electricity that flows in one direction. |
Door Buck | Structural element of a door opening. May be the same element as the frame if frame is structural, as in the case of heavy steel frames. |
Double Glazing | Two parallel sheets of glass with an air space in between. |
Double Tees | T-shaped precast floor and roof units that span long distances unsupported. |
Double-Hung Window | Window sash that slides vertically and is offset in a double track. |
Drainage | (1) In buildings and infrastructure, the system by which excess water is collected, comducted, and dispersed. (2) In landscaping, the capacity of soil to receive and transmit water. |
Dressed Lumber | Lumber having one or more sides planed smooth. |
Drip | Interruption or offset in an exterior horizontal surface, such as a soffit, immediately adjacent to the fascia. Designed to prevent the migration of water back along the surface. |
Drip Line | An imaginary line on the ground described by the outermost branches of a tree. |
Driveway | A vehicular path generally leading from a public street to a structure on private property. |
Dry-Press Process | The process used to make bricks when the clay contains 10 percent or less moisture. |
Drypack | A stiff granular grout. |
Drywall | Generic term for interior surfacing material, such as gypsum panels, applied to framing using dry construction methods, e.g., mechanical fasteners or adhesive. See SHEETROCK brand Gypsum Panels. |
Duct | A hollow tube through which air is circulated. |
Ductile | Capable of being stretched or deformed without fracturing (plastic deformation). |
Ductility | A measure of the capability of a material to be stretched or deformed without breaking. |
Dwelling Unit | An independent living area which includes its own private cooking and bathing facilities. |
Dynamic Load | Any load that is nonstatic. |