Helpful Construction Definitions


AIR BARRIER: material or surface designed to prevent passage of air, but not water vapor.


AIR GAP: a separation between any pipe or faucet conveying water and the flood-level rim of any plumbing receptacle.


AMPACITY: ampere-carrying capacity of a wire.


AMPERE: unit of electrical current. Often abbreviated amp.


ANTI-SIPHON VALVE: valve on a lawn sprinkler that prevents the sprinkler water from backflowing
into the main water supply.


ASBESTOS: a fire and heat-resistant material used in construction until the early 1970s, when it was
discovered to pose health hazards.


ASH DUMP: opening in the floor of a fireplace for ash disposal.


ASPHALT PLASTIC CEMENT: asphalt used to seal roofing materials together.


ATTIC: the space under the roof of a structure but above the top floor.


BACK-FLOW PREVENTER VALVE: see anti-siphon valve above.


BALLOON FRAME: wood frame in which studs are continuous from the sill plate to the top plate of the top floor.


BALUSTER: vertical member under a stair, deck, or porch railing.


BASEBOARD: Any board or molding covering an interior wall where it meets the floor.


BATT: An oblong blanket of fiberglass insulation.


BATTEN: thin wood molding used to cover a joint (usually used with siding).


BAY WINDOW: window that projects outward from the wall.


BEARING WALL: wall that supports a load from above, such as a vertical load of a roof system.


BlTUMIN: substance containing oil or coal-based compounds; (asphalt based roofing material).


BRANCH CIRCUIT: one of several circuits in a building, originating at   the service entrance panel and protected by a separate circuit breaker or fuse.


BRICK VENEER: brick facing over wood or masonry frame.


BRIDGING: bracing between floor joists to prevent twisting of joists.


BRITISH THERMAL UNIT (BTU): amount of heat required to raise the temperature of 1 pound of water by 1 degree.


BUILDING PAPER: a waterproof  heavy paper used in construction of  a roof or wall.


BUILT-UP ROOF: roofing consisting of many alternating layers of asphalt and felt.


BUSS BAR: rectangular metal bar (usually copper) for carrying large electrical current.


BUTT JOINT: joint in which two members meet without overlap or miter.


CAPILLARY: movement of water  through small gaps due to adhesion and surface tension.


CASEMENT WINDOW: window hinged on the side and opening outward.


CASING: inside or outside molding.


CELLULOSE INSULATION: loose-fill insulation consisting of shredded and treated newspaper.


CHECK: cracks in the surface of wood resulting from drying and shrinking of the surface faster then the interior.


CLEANOUT PLUG: a threaded fitting in a pipe or fixture that provides access for cleaning or drainage.


CIRCUIT: two or more wires carrying electricity to lights, receptacles, switches and appliances.


CIRCUIT BREAKER: electromechanical device that opens when the circuit exceeds its electrical capacity.


CLAPBOARD: board used for overlapping as horizontal siding.


CLOSED VALLEY: roof valley where the shingles extend in an unbroken line across the valley intersection.


COLLAR TIE BEAM: a horizontal beam fastened above the upper ends of rafters to stabilize them.


CONDUCTOR: wire intended to carry electrical current.


CONDUIT: metal or plastic pipe that surrounds electrical wires and protects them from physical damage.


CONVECTION: heat transfer through either the natural or forced movement of air.


COUNTERSINK: to sink a nail or screw below the surface.


CRAWLSPACE: a space between the ground and the first floor of a house that allows access for repair of utilities that run under the house.


CRICKET: small roof for diverting  water away from the back side of a chimney.


CRIPPLE WALL: a short wall built upon the foundation of a house that produces a high crawlspace.


DAMPER: an adjustable plate in the flue of a fireplace or furnace that is used to control the draft from the flames.


DAMP-PROOFING: water-proofing a masonry surface to retard capillary action and water leaks.


DEAD LOAD: load imposed on a structure by the weight of the building materials only.


DECAY: deterioration of wood from attack by fungi or insects.


DEW POINT: air temperature at which water vapor begins to condense as either water or ice (frost).


DIELECTRIC UNION: type of connector that insulates two different types of metal pipe to prevent electrolysis.


DIMENSION LUMBER: framing lumber 2 to 5 inches in thickness and up to 12 inches in nominal width.


DIVERSION VALVE: valve in a septic tank system that allows the user to alternate leach lines.


DORMER: vertical window projecting from a roof; gabled dormers have peaked roofs, shed dormers have shed roofs.


DOUBLE GLAZING: insulated window pane formed by two thicknesses of glass with a sealed air space between them.


DOUBLE LUGGING: running two or more electrical circuits off a single lug (terminal or connector).


DOWNSPOUT: pipes leading from the gutters of a roof to the ground and away from the building.


DRAINAGE: gradual flowing of liquids off a surface. Any system to remove liquid waste or rainwater by channeling its flow to a designated area.


DRIP EDGE: material designed to force water to drip away from roof  rakes and eaves.


DUCTS: any conduit for hot air, gas, water, electrical wiring, etc.


EAVES: the lower part of a roof that projects beyond an exterior wall.


EGRESS WINDOW: window whose clear dimensions are large enough that it can serve as a fire exit.


ELEVATION: view of a vertical face of a building.


FASCIA: vertical flat board at the roof eaves, that the gutters are attached to.


FIREBRICK: special clay brick that can be exposed to extremely high temperature change without damage; used in furnaces, fireplaces and similar high temperature areas.


FIRE-STOP: framing member designed to block the spread of fire within a framing cavity.


FLASHING: sheet metal or similar materials used at different points in a structure to prevent water seepage, such as around vent pipes or   chimneys.


FLOOR FURNACE: a ductless  furnace placed directly below a floor that transmits heat only through a grille in the floor.


FLOOR JOIST: a framing piece that rests on the outer foundation walls and interior beams or girders, and supports the flooring above.


FLUE: the opening or passageway in a chimney through which smoke, gases, etc., pass from a building. Any opening or passageway for the elimination of gases or fumes.


FOOTING: foot like projection at the base of a foundation wall, column, pier, etc., used to secure, support, and help eliminate settling or shifting of the wall.


FORCED-AIR FURNACE: furnace that has a fan or blower which forces warm air through the ducts.


FOUNDATION: the part of a building, usually below ground level, that supports the superstructure above it.


FRAMING: wood structure of a building that provides its strength and shape; includes exterior and interior walls, floor, roof, and ceilings.


FRIEZE: in wood construction, the horizontal board between the top of the siding and the soffit.


FROST HEAVE: expansion of the earth due to freezing of interstitial water.


FROST LINE: maximum depth of  freezing in the soil.


FUSE: a short plug in an electric  panel box that interrupts an electrical    circuit when it becomes overloaded.


GIRDER: a large or principal beam used to support concentrated loads or weight at particular points along   its length.


GLAZING: glass or other transparent material used for windows.


GRADE: level of the ground.


GROUNDED WIRE: wire in a circuit that is connected to the ground and serves to return current from the hot   wire back to the ground. Identified by a white insulation jacket.


GROUND FAULT INTERRUPTER: (GFI or GFCI) circuit breaker that trips on leakage of current.


GROUNDING WIRE: bare or green wire in a circuit that connects metal components, such as appliance cabinets, to the ground.


GROUT: very thin mortar applied to masonry joints.


HEADER: beam over a door or window for supporting the load from above.


HEARTH: The stone or brick floor of a fireplace.


HYDRONIC: method of distributing heat by hot water.


I-BEAM: steel whose cross section resembles the letter I.


ICE DAM: ridge of ice at roof eaves or gutters causing snow and ice blockage, and preventing from properly draining.


INFILTRATION: Incursion of outdoor air through cracks, holes and joints.


INSULATING GLASS: factory-sealed double or triple glazing.


JAMB: top and sides of a door or window.


JOINT COMPOUND: material used to finish joints in gypsum drywall. Known as mud.


JOIST: see floor joist.


JUNCTION BOX (J-box): a device in which wires are spliced to bring various electrical circuits together.


KNOB-AND-TUBE WIRING: oldest type of electrical wiring; the knobs serve as insulators, and the ceramic tubes isolate the wiring from neighboring wood.


LATH: perforated base for application of plaster; formerly wood, now usually metal.


LATTICE: framework of crossed strips of wood, plastic, or metal.


LEACH LINE: a gravel-filled subsurface trench extending from a   septic tank; liquid wastes are absorbed into the leach line's soil


LOAD-BEARING WALL: a wall capable of supporting weight.


LINTEL: solid member above a door or window that carries the load above.


LIVE LOAD: temporary load imposed on a building by occupancy and the environment.


MASONRY:  construction consisting of stone, brick, or concrete block.


MEMBRANE ROOF: roofing consisting of a single waterproof sheet.


MITER: to cut at an angle other than 90 degrees.


MOISTURE BARRIER: treated paper or metal that retards or bars water vapor, used to keep moisture from passing into walls or floors.


MORTAR: mixture of cement, sand, and water.


NEUTRAL WIRE: grounded wire.


NON-BEARING WALL: wall or partition that does not carry a load from above.


NOSING: projection of a stair tread beyond the riser.


ON CENTER (OC): framing measurement from the center of one member to the center of the next.


OPEN VALLEY: roof valley where shingles do not cross the valley intersection; flashing does.


PARAPET: a low wall or barrier at the edge of a balcony or roof.


PARGING: a surface coat of cement over masonry to help waterproof it.


PASSIVE SOLAR COLLECTOR: system for collecting solar energy  without use of mechanical devices such as fans or pumps.


PITCH: the angle of slope of a roof. (i.e. 4 inches rise in a 12 inch area equals a 4/12 pitch roof).


PLATE: horizontal framing member at the top or bottom of a wall.


PLENUM: a chamber that can serve as a distribution area for heating or cooling systems, generally located between a false ceiling and the actual ceiling.


POLARITY: the electrical charge, either positive or negative, of an electric service terminal.


PRESSURE-TREATED WOOD: wood that has been injected with preservative under pressure.


RACKING: distortion of a building surface from the rectangular plane.


RADIANT HEATING: method of heating whereby much of the heat transfer is accomplished by radiation through space from warm building,   surfaces such as floors, walls, or ceilings.


RAFTER: roof beam running in the direction of the slope.


REBAR: steel bars used in concrete, to strengthen it and tie it together.


RELATIVE HUMIDITY: amount of   water vapor in air compared with the maximum amount possible, expressed as a percentage.


RETROFIT: to upgrade a structure using modem materials.


RIDGE: highest point of a roof.


RIDGE BOARD: A board running the length of the ridge of the roof, to which rafters are fastened.


RIDGE VENT: continuous, prefabricated outlet ventilator placed over an opening at the ridge of the roof line to allow the release of air.


RISE: vertical increase in one step of a stair.


RISER: vertical board between stair treads. Also a vertical plumbing pipe.


ROLL ROOFING: low-cost asphalt roofing in roll form.


R-VALUE: measurement of a materials resistance to heat.


SASH: frame holding the panes of glass in a window or door.


SEALANT: compressible material used to seal building joints, etc.


SEALED GLASS: panes of glass with a sealed air space between.


SERVICE DROP: service entry wiring from the utility pole to the meter.


SHEATHING: layer of boards over the framing but under the finish.


SHEETROCK: plasterboard compound of a core of gypsum between two sheets of heavy paper.


SHIM: thin, tapered piece of wood or metal, used to level something.


SHINGLE: small, thin piece of material, often tapered, for laying in overlapping rows as in roofing or siding.


SILL: lowest horizontal member in a frame. Also the bottom piece of the window rough opening.


SKYLIGHT: a window in a roof or ceiling.


SLAB-ON-GRADE: concrete slab resting directly on the ground at near grade level.


SOFFIT: underside of a roof overhang, cornice, or stairway.


SPAN: distance between supports.


SPARK ARRESTER: wire mesh device placed atop a chimney to prevent embers from blowing out onto the roof.


STANDING-SEAM: metal roofing technique of folding the upturned edges of adjacent sheets to form a weatherproof seam.


STILE: vertical outside frame member in a door or window sash.


STOOL: interior horizontal, flat molding at the bottom of a window.  


STOP (MOLDING): thin molding for stopping doors on closure or holding window sash in place.


STRINGER: side member of stairway into which the stair treads and risers are attached and set.


STUCCO: a wet plaster finish, specifically designed for exterior use; popular as an outside wall surface or   as a siding material.


STUD: vertical framing member to which wall sheathing and siding are    attached.


SUBFLOOR: first floor laid over the floor joists. The subfloor may also serve as the finish floor.


TAB: exposed portion of an asphalt shingle between the cutouts.


TAPING: finishing gypsum drywall joints with paper tape and joint compound.


TEMPERED GLASS: glass that has been cooled rapidly to produce surface tension; the result is a stronger-than normal glass that shatters into relatively harmless cubical fragments when broken.


TRESHHOLD: a wooden or metal strip under an outside door; the entrance to a building.


THIMBLE: protective device installed in a combustible wall through which a stovepipe passes.


TOE NAILING: nailing a wood joint at an angle for additional strength.


TONGUE AND GROOVE: flooring and sheathing joint in which the tongue of one piece meets a groove in a mating piece.


TRAP: a curved section of drain pipes used under plumbing fixtures to "trap" waste material or debris.


TREAD: horizontal part of a step.


TRUSS: framing structure for spanning great distances, in which every member is purely in tension or compression.


UNDERLAYMENT: sheet material or wood providing a smooth, sound base for the finished floor above.


VAPOR BARRIER: material or surface designed to block diffusion of water vapor.


VERMICULITE: type of insulation.


WATER HAMMER: sound made by supply pipes when water is suddenly stopped by the quick closing of a valve.