Roof Truss Without Bottom Chord

The bottom chord establishes the lower edge of a truss.

Roof truss without bottom chord.

There may be an overhang at the end of a cantilever. Then there is the top chord or rafters that are angled to make the roof pitch. Finally there are the gussets that hold the framed truss together. The bottom chord of the cap truss is typically moved up 1 1 2 for 2x4 continuous lateral restraints over the flat top chord of the base truss or the thickness of whatever material may be used 3 4 for plywood osb etc.

For traditionally spaced trusses the bottom chord is cut out of 2x4 or 2x6 dimension lumber but can also be cut out of 2x8 2x10 2x12 and even lvl material for roof trusses. They will serve as rafters. The bottom chord therefore carries combined stress of both tension and bending of the truss. See gusset construction below.

The top chord or chords are the single most important elements of a roof truss. Bottom chords is at least 3 12 or the bottom chord pitch is no more than half the top chord pitch. For instance additional chords can be installed low enough to recreate trusses but high enough to accommodate a raised vehicle. This is the distance of the bottom chord of the truss from outside overhang of bearing wall to outside of the other bearing wall.

The cap truss is very similar to a gable truss with webs transferring loads vertically into the base truss below it. There are three parts to the roof truss that you have to know. Factors that affect truss pricing and cost. The span in short is the length of the bottom of the truss.

The bottom chord is also called a scissors truss. There are a number of truss styles that do not use a horizontal bottom chord the scissor truss for instance. The bottom chord then extends past the bearing wall. Factors that determine the size of the bottom chord include on center spacing dead loads.

And using steel as a construction material can help to redirect the tensions through materials more. The bottom chord will have breaks in it. Flat the most economical flat truss for a roof is provided when the depth of the truss in inches is approximately equal to 7 of the span in inches. The bottom chord typically carries combined tension and bending stresses.

The chord s length must match the width of the roof. A cantilever truss allows for level coverage past the exterior wall such as patios porches entryways and other offsets in the building elevation by moving one or both bearings inward from the end of the bottom chord up to 1 4 of the span. Some spans have a lower rate per foot than others. About the bottom chord.

On a typical truss they will be made from 2 x 4 s.