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Below are terms related to homes and their systems and components. You may encounter these terms in your Home Inspection Report or when communicating with other inspectors or contractors about your home.

A - B

ABS (acrylonitrile butadiene styrene): Rigid black plastic pipe used only for drain lines.

A/C condenser: The outside fan unit of the air-conditioning system that removes the heat from the Freon® gas and turns the gas back into a liquid, then pumps the liquid back to the coil in the furnace.

A/C disconnect: The main electrical ON-OFF switch near the A/C condenser.

access panel: A closure device or door used to cover an opening into a duct, wall, ceiling or enclosure near a fixture that allows access for servicing, such as for the plumbing or electrical system.

accessible: In the opinion of the inspector, can be approached or entered safely, without difficulty, fear or danger.

accessory structure: A building on a property in addition to the primary building.

AFCI (arc-fault circuit interrupter): A device intended to provide protection from the effects of arc faults by recognizing characteristics unique to arcing and functioning to de-energize the circuit when an arc fault is detected.


aggregate: Crushed stone, slag or water-worn gravel that comes in a wide range of sizes and is used to surface built-up roofs.

air duct: Ducts typically made of sheet metal that carry cooled or heated air to all rooms.

air filters: Adhesive filters made of metal or various fibers that are coated with an adhesive liquid to which particles of lint and dust adhere. Air filters remove as much as 90% of dirt if they do not become clogged. The more common filters are of the disposable type.


air gap (drainage): The unobstructed vertical distance through free atmosphere between the outlet of the waste pipe and the flood-level rim of the receptacle into which the waste pipe is discharged.


air handler: Components that blow air through ductwork for heating, cooling and/or ventilation purposes.

air-admittance valve: Pressure-activated, one-way mechanical vent that is used when venting through the building?s roof structure is not available.

alligatoring: An oxidized condition of paint or aged asphalt that has lost its volatile oils due to exposure to sun and solar radiation, which is the ultimate result of the paint or asphalt's limited tolerance to thermal expansion and contraction. Alligatoring is characterized by a coarse, checked pattern that results when a new paint coating slips over the old coating to the extent that the old coating can be seen through the fissures, producing a pattern of cracks resembling an alligator hide.

anchor bolts: In residential construction, the bolts used to secure a wooden sill plate to a concrete or masonry floor or wall. In commercial construction, anchor bolts fasten columns, girders and other members to concrete or masonry, such as the bolts used to anchor sills to a masonry foundation.

anti-siphon: A device that prevents wastewater from being drawn back into supply lines and possibly contaminating the water supply.

appliance: A household device operated by use of electricity or gas. Not included in this definition are components covered under central heating, central cooling or plumbing. In commercial applications, equipment other than industrial that is installed or connected as a unit to perform one or more functions.


apron: A trim board that is installed beneath a window sill.


arc-fault circuit interrupterSee AFCI. 


architectural shingles: Shingles that have added dimensionality because of extra layers or tabs, giving them a shake-like appearance. Also called laminated shingles and three-dimensional shingles.


asbestos: A common form of magnesium silicate and naturally occurring mineral fiber that was used in various construction products and older homes because of its stability and resistance to fire. Asbestos is also the name given to certain inorganic minerals in their fibrous form. Although asbestos is fire-resistant, it is considered a serious health hazard because its extremely fine fibers are easily inhaled, and exposure to these fibers over a long period of time has been linked to cancers of the lung and the lung-cavity lining, as well as asbestosis, which is a severe lung impairment. Homeowners should be alert for the existence of friable asbestos (that which is readily crumbled or brittle) and always seek professional advice before disturbing it.


asphalt: A dark brown to black, highly viscous hydrocarbon produced from the residue left after the distillation of petroleum. Asphalt is used on roofs and highways as a waterproofing agent.


astragal: A molding that is attached to one of a pair of swinging doors against which the other door strikes.


attic access: An opening that is placed in the drywalled ceiling of a home providing access to the attic.


attic ventilators: In houses, the screened openings provided to ventilate an attic space. They are located in the soffit area as inlet ventilators and in the gable end or along the ridge as outlet ventilators. They may also consist of power-driven fans used as an exhaust system.


automatic sprinkler system: An automated sprinkler system activated for fire-protection purposes.


awning window: A window with hinges at the top that allow it to open out and up.



backfill: The slope of the ground adjacent to a house. The replacement of excavated earth into a previously excavated area, such as a trench around and against a basement foundation. In carpentry, the process of fastening together two pieces of board by gluing blocks of wood in the interior angle.


backflow: Movement of water (or other liquid) in any direction other than that intended.


backflow preventer: A device or means to prevent backflow of contaminated water into the potable water supply.


backsplash: The raised portion of tile, stone, etc., located at the rear of a wall-mount sink or lavatory that is installed to protect the wall behind.


balcony: An exterior floor projecting from and supported by a structure without additional independent supports.


balusters: The vertical members in a railing installed between the top rail and bottom rail or stair treads.


band joist: Dimensional lumber used as a perimeter joist of a building's framing.


barrel roof: A roof design that in cross-section is arched.


base flashing: The upturned edge of a watertight membrane formed at a roof's termination point by the extension of the felts vertically over the cant strip and up the wall for a varying distance, where they are secured with mechanical fasteners.


base molding: Molding used to trim the upper edge of interior baseboard.


base ply: An asphalt-saturated and/or -coated felt installed as the first ply with 4-inch laps in a built-up roof system under the subsequent courses of felt, which can be installed in a shingle-like fashion.


base shoe: Molding used next to the floor on interior base board, sometimes called a carpet strip.


baseboard: Wood or vinyl installed around the perimeter of a room to cover the space where the wall and floor meet; a board placed against the wall around a room next to the floor to properly finish the area between the floor and the plaster.


baseboard heat: An electric or hot-water heating system whose heating unit is located along the perimeter of the wall where the baseboard would normally be located.


basement: That portion of a building that is partly or completely below grade.


basement wall: A wall that is mostly below grade.


basket strainer: Basket-shaped strainer for a sink drain that has holes which allow water to drain while catching food and other solids. Can also be closed to fill the sink with water.


bathroom: A room containing plumbing fixtures, including a lavatory/sink, water closet, urinal, bidet, bathtub and/or shower.


batt insulation: Strips of (typically) fiberglass insulation that fit between studs and other framing.

batten: Narrow strips of wood used to cover joints and/or as decorative vertical members over plywood or wide boards.

bay window: A window space projecting outward from the walls of a building, typically square or polygonal in plan.

bead: In glazing, an applied sealant in a joint, irrespective of the method of application, such as caulking bead, glazing bead, etc.; also, a molding or stop used to hold glass or panels in position.

beam: A supporting member of wood or steel; structural support member (of steel, concrete, lumber, etc.) transversely supporting a load that transfers weight from one location to another.


bearing wall: A wall that supports any vertical load in addition to its own weight.


bedroom: A room used for sleeping purposes.


below grade: Describes the portion of a building that is below ground level.


bidet: A toilet-like plumbing fixture designed to promote posterior hygiene; not a toilet.


bifold doors: Doors that are hinged in the middle to allow them to open in a smaller area than standard swing doors, typically used for closet doors in residential installations, and kitchen doors separating the kitchen from the dining area in commercial installations.


bitumen: Refers to any of a variety of mixtures of hydrocarbons occurring naturally or obtained through the distillation of coal or petroleum. (See also coal tar pitch and asphalt).


blankets: Fiberglass or rock-wool insulation that comes in long rolls 15 or 23 inches wide.


blister: An enclosed raised spot evident on the surface of a building, mainly caused by the expansion of trapped air, water vapor, moisture or other gases.


blown-in insulation: Fiber insulation in loose form used to insulate attics and existing walls where framing members are not exposed.


board and batten: A method of siding in which the joints between vertically-placed boards or plywood are covered by narrow strips of wood.


bonding: The permanent joining of metallic parts to form an electrically conductive path that ensures electrical continuity, and the capacity to safely conduct any fault current likely to be imposed.

bonding strip (electrical): A thin strip of metal inside armored or BX cable, which is meant to back up the primary ground.

bottom chord: The lower or bottom horizontal member of a truss.

bottom plate: The 2x4s or 2x6s that lay on the subfloor upon which the vertical studs are installed. Also called a sole plate.

bow: A curve, bend, warping or other deviation from flatness in glass or wood.

box cornice: A cornice completely closed with trim work.

branch circuit: Wiring that runs from a service panel or sub-panel to outlets; the circuit conductors between the final over-current device protecting the circuit and the receptacle(s)/outlet(s). Branch circuits are protected by fuses or breakers at the panel.

breaker box: A metal box that contains circuit breakers or fuses that control the electrical current in a home.

breaker panel: The electrical box that distributes electric power entering the home to each branch circuit (each plug and switch) and composed of circuit breakers.

breezeway: A covered/roofed and closed- or open-sided passageway connecting two structures, such as a house and a garage.

brick ledge: Part of the foundation wall where brick veneer rests.

brick lintel: The metal angle iron that brick rests on, typically found above a window, door or other opening.

brick mold: Trim used around an exterior door jamb onto which siding butts.

brick tie: A small, corrugated metal strip (1x6 to 8 inches long) nailed to wall sheeting or studs that are inserted into the grout mortar joint of veneer brick to hold the veneer wall to the sheeted wall behind it.


brick veneer: A facing of brick laid against and fastened to the sheathing of a frame wall or tile wall construction.

bridging: Small wood or metal members that are inserted in a diagonal position between floor joists at midspan to act as both tension and compression members for the purpose of bracing the joists and spreading the action of loads.

browncoat: The coat of plaster directly beneath the finish coat. In three-coat work, the browncoat is the second coat.


BTU (British thermal unit): A measure of the capacity of a heating or cooling system; the amount of heat energy required to raise the temperature of 1 pound of water through a change of 1 degree.


buckling: The bending of a building material as a result of wear and tear or contact with a substance, such as water.


building brick: Brick for building purposes not especially treated for texture or color, formerly called "common brick." It is stronger than face brick.

building code: Minimum local and/or state regulations established to protect health and safety, which apply to building design, construction, rehabilitation, repair, materials, occupancy and use; community ordinances governing the manner in which a home may be constructed or modified.


building envelope: The enclosure (exterior walls and roof) that defines the heated/cooled area of a building.


built-in: Permanently installed.


built-up beam: Beam or girder created by sistering or scabbing two or more pieces of lumber together. Also called a build-up girder.


built-up roof, roofing (BUR): Generally used on flat or low-pitched roofs, a roofing system composed of three to five layers of asphalt felt laminated with coal tar, pitch or asphalt, and finished on top with crushed slag or gravel.


bullnose drywall: Rounded drywall corners.

bundle: A package of shingles that contains three, four or five bundles per square.

bushing: A pipe fitting for joining pipes having different diameters. A bushing is threaded on the inside and outside.


butt joint: The junction where the ends of two timbers or other members meet in a square-cut joint.


butterfly roof: A roof assembly that pitches sharply from either side toward the center.


BX cable: Armored electrical cable wrapped in a galvanized-steel outer covering. A factory assembly of insulated conductors inside a flexible metallic covering. It can be run anywhere except where exposed to excessive moisture. It should not be run below grade. It must always be grounded and uses its armor as an equipment ground. It is difficult to pull out old wires or insert new ones.


bypass doors: Doors that slide by each other, commonly used as closet doors.

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