Allowable Stress Increase
A percentage increase in the stress permitted in a member based on the length of time that the load causing the stress acts on the member. The shorter the duration of the load, the higher the percent increases in allowable stress.
The uppermost point of a truss.
A push (compression) or pull (tension) acting along the length of a member. Usually measured in pounds, kips (1,000 lbs.) or tons (2,000 lbs.), or metric equivalent.
The axial force acting at a point along the length of a member divided by the cross-sectional area of the member. Usually measured in pounds per square inch.
Timber sections spanning trusses to support roof covering.
A structural support, usually a wall, that occurs at the top or bottom chord or between the end points of a roof or floor truss.
A measure of the bending effect on a member due to forces acting perpendicular to the length of the 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.
The force per square inch of area acting at a point along the length of the member, resulting from the bending moment applied at that point. Usually measured in pounds per square inch or metric equivalent.
A horizontal or inclined (e.g., Scissors Truss) member that establishes the lower edge of a truss. In a conventional system, this is the ceiling joist.
Slight vertical cut at the outside edge of truss bottom chord made to ensure uniform span and tight joints- usually 1/4 inch.
An upward vertical displacement built into a truss bottom chord to compensate for deflection due to dead load.
Extension of the bottom chord beyond its support, exclusive of overhang.
A lengthwise separation of wood fibers, usually extending across the rings of annual growth, caused chiefly by strains produced in seasoning.
Horizontal distance between interior edges of supports.
The combination of axial and bending stresses acting on a member simultaneously, such as occurs in the top chord (compression + Bending) or bottom chord (tension + bending) of a truss.
Superimposed load centered at a given point (e.g., roof-mounted air conditioner, furnace.)
Pre-punched metal toothed connectors located at the joints and splices of a truss and designed to hold the forces, which occur, at those locations.
Infill rafter installed to continue the roof line- fixed to valley board in valley construction.
Any permanent load such as the weight of roofing, flooring, sheathing, insulation or ceiling material, as well as the weight of the truss itself.
Downward vertical movement of a truss (when in place) due to dead and live loads.
The dead and live loads which a truss is engineered to support.
Engineer Certified Drawing
A truss design where loading requirements, lumber species, sizes, grades and connector plate requirements are detailed and a certified engineer's seal is affixed.
Usually a multiple-ply truss designed to carry other trusses over an opening.
Point on a truss at which the top and bottom chords intersect.
See butt cut.
Infill rafter installed to continue the roof line- fixed from wall plate to hip board in hip end construction.
See Panel Point
A member placed and connected at right angles to a chord or web member of a truss.
A lumber filler placed horizontally from the end of an overhang to the outside wall to form a soffit.
Any loading which is not of a permanent nature (e.g., snow, wind).
Moisture Content of Wood
The weight of the moisture in wood expressed as a percentage of its oven-dry weight.
Vertical distance from bottommost part of the bottom chord to uppermost point on peak.
The extension of the top chord of a truss beyond the heel measured horizontally.
The chord segment defined by two adjacent joints.
The centerline distance between joints measured horizontally.
The point where a web or webs intersect a chord.
Point on truss where the sloped top chords meet.
Inches of vertical rise for each 12 inches of horizontal run.
Top chord end cut to provide for vertical (plumb) installation to fascia (face trim board).
Vertical overall measurements at the end of a truss where the top and bottom chords meet.
Point on triangular Fink or Howe truss where the webs connect to the top chord.
Point on triangular Fink truss where the webs connect to the bottom chord.
A horizontal member attached to and placed perpendicular to the truss top chord to support the roofing.
Forces acting on a truss, through its support, that are equal but opposite to the sum of the dead and live loads.
Line formed by truss apexes.
Vertical distance from bottommost part of the bottom chord to inside of the peak.
Additional timber connected to a truss to effect a splice, extension or general reinforcement.
Detailed drawings of roof truss or roof framing showing critical dimensions such as span, overhang, cantilever, slope, etc.
Centerline distance between trusses, usually 24" O.C. (on center)
Horizontal distance between outside edges of the support.
(Top and bottom chord splice) The point at which two chord members are joined together to form a single member. It may occur at a panel point or between panel points.
End of top chord cut perpendicular to slope of the member.
Truss with the same configuration of members and design loading occurring on each side of truss centerline.
An inclined or horizontal member that establishes the upper edge of a truss- rafter in conventional frame.
A pre-built component that functions as a structural support member. A truss employs one or more triangles in its construction.
Metal component designed to provide structural connection of trusses to wall plates to resist wind uplift forces.
Members that join the top and bottom chords to form the triangular patterns that give the truss strength.