There are two main types of timber roof trusses.
Roof truss chord.
The chord size and web configuration are determined by span load and spacing.
The bottom chord which is the bottom of the framed truss.
Hip end trusses that are supported by.
Some common trusses are named according to their web configuration such as the king post fan fink or howe truss.
All truss designs are optimized to provide the most economical configuration for the specific application.
End trusses close in the end of a building and provide a nailing surface for the upper end wall or rigid sheathing.
The more complex the truss framework is the greater quantity of these joints will be required.
There are three parts to the roof truss that you have to know.
The parallel chord or flat truss gets its name from having parallel top and bottom chords.
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.
Truss that supports creeper trusses and creates hip roof plane.
These trusses are positioned on the top plate of the endwall so the entire bottom chord is supported by the wall.
Any weight imposed on the end truss is directly transferred to the endwall which transfers the weight to the foundation.
Complying with the erection tolerances specified in sbca s bcsi b1 summary sheet is critical to achieving an acceptable roof line.
Variance from the design dimensions is also allowed.
Then there is the top chord or rafters that are angled to make the roof pitch.
Bottom chords is at least 3 12 or the bottom chord pitch is no more than half the top chord pitch.
For example table 3 5 1 allows identical trusses to vary in span by as much as 1 2 in.
Closed in which the bottom chord is horizontal and at the foot of the truss and open in which the bottom chords are raised to provide more open space also known as raised bottom chord trusses.
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Hip end trusses that are supported by hip truss and creates hip plane.
Similar to the raised heel truss this type also creates a vapor barrier creating great insulation characteristics.
And in height by as much as 1 4 in.
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See gusset construction below.
The same thing is true for the bridge of the truss.
Closed open distinction is used in two ways to describe truss roofs.
Truss that creates roof planes and does not support other trusses truss that creates hip plane by truncating and allowing hip jacks truss top chords to fly over.
It is most often used for roof construction.
Finally there are the gussets that hold the framed truss together.
The dropped chord variant is composed of a convention truss with a secondary chord truss suspended below to help reduce uplift.
Dropped chord roof truss.
