B Definitions

Definition Categories

Balloon framing

Balloon framing is a building system where walls extend from the foundation to the ceiling joists. Intermediate floor joists are attached to the walls and are often supported by a ledger. Balloon framing is rare in modern residential construction.



A baluster (also called a picket) is a vertical piece found in guard rails and handrails that supports the rail and provides protection against occupants falling through or being caught between the balusters.


A basement, broadly defined, is an area of the building below ground. Minimum ceiling heights apply to basements. See Chapter 3. An area below ground with less than the minimum ceiling height may be considered a crawl space. A basement often has a concrete floor, but this is not required by the IRC. A basement is usually not counted as a story, but it could be in some cases. See Chapter 1 and the IRC to determine if a basement is counted as a story above grade.

Basement wall

A basement wall is a wall with at least (≥) 50 percent of its area below grade (covered by earth on the outside) and encloses conditioned space.

Bathtub (whirlpool)

A whirlpool bathtub is a bathtub equipped with a pump and water circulation system and is designed to be filled and emptied with each use. These bathtubs are usually located in bathrooms. They are also called hydromassage tubs and are sometimes referred to by the brand name Jacuzzi®.


(1) A batten is a vertical wood strip applied at the seam between two pieces of vertical siding, such as 4×8 panel siding. When used with siding material, such as 1×6 vertical boards, the siding is called board and batten.

(2) A batten is a wood strip, usually a 1×2, applied on a roof to help secure roof coverings such as tile and slate.

(3) A batten is a wood strip applied to framing or to masonry as a place to attach drywall or lathing for plaster. In this application it is often called a furring strip.

Bend (Elbow)

A bend is a drainage fitting used to change the direction of flow. A bend is often called an elbow. Bends are available as a single fitting with two openings and some are available as a double fitting with three or more openings. Some bends have inlets in addition to the openings. Use vent bends only in the dry vent sections of vent pipes. Quarter bends are sometimes called short sweeps in plastic pipes. See the definition of sweep. Quarter bends with a longer turn radius are sometimes called long turn quarter bends or long sweeps. Bends are made with the following angles.


Blocking usually consists of pieces of wood that are used to connect, reinforce, or fill spaces between studs, joists, and rafters. Blocking may be installed at the ends of floor joists to help keep the joists from twisting and to provide support for wall systems above. Blocking may be installed between studs, joists, and rafters to provide support for wood structural panels such as plywood. Blocking is sometimes installed between studs that have been bored or notched to help distribute the load between the studs and to help keep them from twisting.

Bonding Metallic

Bonding Metallic components are bonded if they are physically and electrically connected together. Components are bonded when a bonding wire connects them together. Example: a bonding wire should connect a swimming pool motor and nearby metal parts of the electrical supply system. Components are bonded when there is an electrically conducting connection between metal parts. Example: metal conduit should be electrically and mechanically connected where it enters a panelboard cabinet.  Bonded metallic components are part of an electrically conductive path that will safely conduct current imposed by a ground fault. Example: when metal conduit containing a damage wire becomes energized, this is a ground fault. A proper bonding connection will conduct the fault current on the conduit safely to ground and allow proper operation of the circuit breaker or fuse. Otherwise, a person touching the energized conduit could become the current’s path to ground and that person could receive a dangerous shock or the current flow could generate enough heat to start a fire.

Braced wall line

A braced wall line (also called a shear wall) is a wall that is secured and braced to resist movement (racking) during high winds and seismic events. Bracing usually consists of wood panels, metal straps, drywall, or a combination of materials installed as described in Chapter 6.

Branch circuit

A branch circuit begins at a circuit breaker or fuse in a panelboard and conducts electricity to where it is used. A branch circuit can serve one device, such as an oven, or it can serve multiple devices such as receptacles and light fixtures.

Branch circuit (general lighting)

A general lighting branch circuit is one that serves multiple light fixtures and receptacles. This includes lights and receptacles in places such as bedrooms, living areas, hallways, garage and the home’s exterior.

Branch drain

A branch drain is a drainage pipe that takes material from two or more plumbing fixtures to a stack or to the building drain. It is also called a fixture branch. Branch vent A branch vent connects individual vents to a vent stack or stack vent.

Braze (Brazing)

Brazing is a method of joining metal pipe (such as copper and brass) at temperatures exceeding 1,000° F. Brazing is sometimes called silver soldering because it uses a silver alloy as the brazing material. Brazed joints are stronger than soldered joints.


Bridging is sometimes installed near the center of fl oor joists to help hold the joists in place and to help keep them from twisting. Bridging is usually 1×4 wood installed in an X pattern, or wood blocks that are the same depth as the joist, or metal bridging brackets. Bridging is required only on larger joists (deeper than 2×12), but is often installed on other depth floor joists.

Building drain (sub-drain)

The building drain is usually the lowest horizontal drain pipe in the building and collects material from branches and stacks. It extends to 30 inches beyond the foundation where it connects with the building sewer. A building with fixtures below the building drain (such as in a basement) has a building sub-drain. Material in a sub-drain must be pumped up to the building drain.

Building or thermal envelope

The building or thermal envelope is the conditioned (heated and cooled) area of the building. The envelope boundary between conditioned and unconditioned space includes walls, ceilings, floors, basement walls and slab-on-grade foundations.

Building sewer

Building sewer usually refers to the pipes beginning at the building drain and ending at the public sewer or septic tank.


A buttress is a vertical column of masonry that helps a wall resist horizontal (lateral) loads.