Provides support for non-insulated 8" siding at panel overlaps (joints), and behind panels at corners to ensure a smooth installation.
Backerboard
Rigid board used beneath tile, as the base layer for acoustical ceiling tile or as the first layer in a multiple-layer wall system. Base ply wall panels are used by keeping the long edges parallel to the wall studs, unless the wall height is more than 97 inches or you are using decorated wall panels. Face ply, second layer and base ply panels can't fall in the same place, which would weaken the joint, so they are staggered. Base ceiling panels are fastened with the long edges perpendicular to the to the ceiling joints or framing. Face ply is installed over this with the long edges parallel to the ceiling joist and are fastened though the base ply panels into the joists.
Backfill
Soil, stone or other material moved up against a foundation to solidify and support the foundation structure of a newly built house or replacing the excavated earth around and against the foundation. Compacted earth retains its shape so that water will flow away from the foundation wall. For that reason, backfill should be a blend of earth and stone and without materials that would deteriorate easily.
Backflow
A reverse flow of water or other liquids into the water supply pipes, caused by negative pressure in the pipes.
Backflow preventer
Plumbing device which prevents the backflow of water (reversing its flow and returning to the supply system) by using a check valve, which permits flow in only one direction by using a hinged flapper or guided poppet that opens when the flow is going in one direction but will close if the direction reverses. An air gap, which is a vertical distance between the outlet of the supply and the overflow rim of the fixture into which the water flows. Water, under pressure, can pass over an air gap but cannot return to the supply. Plumbing codes usually require that backflow preventers are installed between the water main and the branch connections to individual service.
Background concentration
The level of a contaminant present before the introduction of a new source.
Backhand welding
Form of welding with the torch facing the weld and being moved backward as the weld bead moves forward.
Backhearth
The part of the hearth inside the fireplace.
Backhoe
Piece of heavy equipment, used in construction, which has a bucket suspended on a movable boom.
Backing
(1) Substance used behind a facing to add strength, stiffness or structural support. (2) Block wall serving as a base for brick wall by using an occasional header brick to tie the brick wall to the backing. (3) Supporting of the weld metal during welding by adding material to the back side of the root.
