Glossary of Construction Terminology



GFCI, or GFI, Ground Fault Circuit Interrupter - A sensitive plug designed to shut off all electric current. Used in bathrooms, kitchen, exterior outlets, garage outlets and other wet areas. Has a small reset button on the device.

gable – The end, upper, triangular area of a home, beneath the roof.

galvanize – To coat a metal with zinc by dipping it in olten zinc after cleaning.

gang nail plate – A steel plate attached to both sides at each joint of a truss. Sometimes called a fishplate, or gusset.

gate valve – A valve that lets you completely stop – but not modulate – the flow within a pipe.

General Contractor – A contractor responsible for all facets of construction of a building or renovation.

gas lateral – The trench or area in the yard where the gas line service is located, or the work of installing the gas service to a home,

girder – A main beam upon which floor joists rest, usually made of steel or wood.

glazing – The process of installing glass, which commonly is secured with glazier’s points and glazing compound.

globe valve – A valve that lets you adjust the flow of water to any rate between fully on and fully off. Also see gate valve.

gloss enamel – A finishing paint material. Forms a hard coating with maximum smoothness of surface and dries to a sheen or luster.,

glulam, glued laminated beam – A structural beam composed of wood laminations or lams. The lams are pressure bonded with adhesives to attain a typical thickness of 1-1/2”.

grade – ground level, or elevation at any given point. Also the work of leveling dirt. Also the designated quality of a manufactured piece of wood.

grade beam – A foundation wall that is poured at level with or just below the grade of the earth. An example is the area where the 8’ or 16’ overhead garage door “block out” is located, or a lower (walk out basement) foundation wall is poured.

grain – The direction, size, arrangement, appearance, or quality of the fibers in wood.

grid – The completed assembly of main and cross tees in a suspended ceiling system before the ceiling panels are installed. Also the decorative slats installed between glass panels.

ground system – The connection of current carrying neutral wire to the grounding terminal in the main switch which in turn is connected to a water pipe. The neutral wire is called the ground wire.

ground rod – Rod used to ground an electrical panel.

grout – A cement mortar mixture commonly used to fill joints and cavities of masonry.

gunite – A construction material composed of cement, sand or crushed slag and water mixed together and forced through a cement gun by pneumatic pressure, used in the construction of swimming pools.

gusset – A flat wood, plywood, or similar type member used to provide a connection at the intersection of woo d members. Most commonly used at joints of wood trusses. They are fastened by nails, screws, bolts or adhesives.

gutter – Metal trough at the eaves of a roof to carry rain water from the roof to the downspout.

guy wire – A strong steel wire or cable strung from an anchor on the roof to any tall slender projection for the purpose of support.

gyp board – Drywall, wall board or gypsum, a panel made with a core of chalk-like gypsum rock, which is used to cover interior walls and ceilings.

gypsum plaster – Gypsum formulated to be used with the addition of sand and water for base-coat plaster.


hardware – Metal accessories such as door knobs, towel bats, toilet paper holders, etc.

hatch – An opening in a deck, floor or roof. The usual purpose is to provide access from inside the building.

Hazard Insurance – Insurance for a building while it is under construction.

header – Framing members over windows, doors or other openings

hearth – The fireproof area directly in front of a fireplace. The inner or outer floor of a fireplace, usually made of brick, tile or stone.

heat pump – A mechanical device which uses compression and decompression of gas to heat and/or cool a house.

heartwood – The wood extending from the pith to the sapwood, the cells of which no longer participate in the life processes of the tree.

heel cut – A notch in the end of a rafter to permit it to fit flat on a wall and on the top, doubled, exterior wall plate.

hermetic seal – Vacuum seal, between panes of a dual-paned window. Failure of a hermetic weal causes permanent fogging between the panels of the IGU.

hip – The external angle formed by the meeting of two sloping sides of a roof.

hip roof – A roof that rises by inclined planes from all four sides of a building.

home run – The electrical cable that carries power from the main circuit breaker panel to the first electrical box, plug, or switch in the circuit.

honey combs – The appearance concrete makes when rocks in the concrete are visible and where there are void areas in the foundation wall, especially around concrete foundation windows.

hose bib – An exterior water faucet.

hot wire – A wire that carries electrical energy to a receptacle or other device, in contrast to the neutral, which carries electricity away again. Normally the black wire.

humidifier – An appliance normally attached to the furnace, or portable unit device designed to increase the humidity within a room or a house by means of the discharge or water vapor.

HVAC – An abbreviation for Heating Ventilation and Air Conditioning.


IIC – A new system utilized in the Federal Housing Administration recommended criteria for impact sound insulation.

INR, Impact Noise Rating – A single figure rating which provides an estimate of the impact sound insulating performance of a floor-ceiling assembly.

I-beam – A steel beam with a cross section resembling the letter I. It is used for long spans as basement beams or over wide wall openings, such as a garage door, when wall and roof loads are imposed on the opening.

I-joist – Manufactured structural building component resembling the letter I. Used as floor joist, and rafters.

incandescent lamp – A lamp employing an electrically charged metal filament that glows at white heat. A typical light bulb.

Indemnification Clause – Provision in a contract in which one party agrees to be financially responsible for specified types of damages, claims, or losses.

infiltration – The passage of air from indoors to outdoors and vice versa; term is usually associated with drafts from cracks, seams or holes in buildings.

inside corner – The point at which two walls form an internal angle, as in the corner of a room.

insulating glass unit, IGU – Two or more lites of glass spaced apart and hermetically sealed to form a single-glazed unit with an air space between each lite.

insulation – Any material high in resistance to heat transmission that, when placed in the walls, ceiling, or floors of a structure, and will reduce the rate of heat flow, and the transmission of sound.

insulation board, rigid – A structural building board made of coarse wood, or cane fibe in ½” and 25/32” thickness. It can be obtained in various size sheets, in various densities, and with several treatments.

insulation, thermal – Any material high in resistance to heat transmission that when placed in the walls, ceiling, or floors of a structure, will reduce the rate of heat flow.

interior finish – Material used to cover the interior framed areas of walls and ceilings.