Beam Pocket - Void or cut-out built into truss to allow beam support.
Bearing - Structural support, usually a beam or wall, that is designed by the building designer to carry the truss reaction loads to the foundation.
Bending Moment - Measure of the bending effect due to the live load and dead load on a given truss chord member. The bending moment at a given point along a member equals the sum of all perpendicular forces, either to the left or right of the point, times their corresponding distances from the point.
Bending Stress - Force per square inch of area acting at a point along the length of a member resulting from the bending moment applied at the point. Usually measured in pounds per square inch (psi) or metric equivalent.
Bird's Mouth Cut Notch - formed by a plumb and seat cut at the eave end of a rafter that allows the rafter to sit on the top plate.
Board - Lumber less than 2" in nominal thickness.
Board Foot - Unit of measurement represented by a board 1' long, 1' wide, and 1" thick.
Abbreviation ft. b.m., bd. ft., or fmb. In finished or surfaced lumber, the board-foot measure is based on the nominal size. In practice, the working unit is 1000 board feet.
Abbreviation M bd. ft., M.B.M., or M.B.F.
Bob-Tail - A term used to describe a gable shaped truss that is clipped at the end.
BOCA - Building Officials and Code Administrators International (Model Building Code).
Bottom Chord - The main member of a truss running along its lower side between supports and usually carrying combined tension and bearing.
Bottom Chord Bearing - Bearing condition of a parallel chord truss that bears on its bottom cord.
Bottom Chord Upset - See Butt Cut.
Bottom Plate - Bottom horizontal framing member of a stud wall.
Bow - Distortion of a piece of lumber in which there is a deviation in a direction perpendicular to the flat face from a straight line end to end of the piece.
Bracing - See Permanent Bracing and Temporary Bracing.
Break Point Joint - Top chord joint of a hip truss where the sloping chord member and horizontal member meet.
Bridging - Wood or metal members that are placed between trusses and joints in an angled position intended to spread the loads.
Built-Up Beam - Single member composed of two wood members having the same thickness but not necessarily the same depth, which provides greater load carry capability as well as lower deflection (e.g., garage door, stairwell and fireplace header).
Build-Up Roof - Roofing composed of three to five layers of asphalt.
Butt Cut - Vertical cut at outside edge of a truss bottom chord to insure uniform nominal span and tight joints, typically 1/4".
Butt Joint - The interface at which the ends of two members or other members meet in a square cut joint.
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