Typical Site Built Truss Questions

Started by Alberta Curt, June 24, 2008, 10:22:33 PM

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Alberta Curt

Getting closer to having to do the trusses and I'm scared stiff.  I have the following questions:

1. Plans call for 2x6 construction and I've come up with 16.5' for the truss (20 ft wide with 1'-4" eave extension).  Does the truss have to be one piece or can it be two pieces supported by a gusset?

2. Do I double up the trusses on the ends (ridge and gable?)?

3. I have read conflicting reports on spacing.  16 or 24"?

4. Vent block shows 22 1/2" in length.  How does this correspond to the truss spacing?


John Raabe

#1
I see that you have the 20' wide 1-1/2 story plans. The upper 2x6 in the truss diagram is strongest if full length one-piece.  If you used 16' material then the eaves would be square cut, which might be OK depending on gutters. It would be almost a 16" overhang and you wouldn't have to cut down 18' material.

All the roof trusses are 24" o/c. Thus the vent blocking cut to fit between them. You don't need to double the gable end trusses. Do this only where an extra load in encountered (dormers or support for a ridge beam).

You should also check on locally made prefab trusses. These may cost less than making them yourself as the truss Co. will make them with smaller material most likely. They engineer for the local loads and can often deliver the trusses to the top wall plates.
None of us are as smart as all of us.


Alberta Curt

Thanks John. 

You mention I would still have 16" overhang if I used 16 footers.  Checked my math and I was wrong. 

I'd love to have the trusses built locally except I am quading all of my material 1/2 mile through the bush until we build an access road later in the year.

John Raabe

Yep, well that's the reason I did the site built truss diagram. Sometimes you just gotta do it yourself. ::)
None of us are as smart as all of us.

Alberta Curt

Another question.......

on the gable rafters, does one frame from the wall top plate to the attic joist?  I have assume so up to this point, but am a little unclear on how to proceed.


John Raabe

Yes, if I understand the question properly.

I would install the gable end truss (that carries the roof load) and then fill in the wall framing below. You could also leave off the outboard gussets on these end wall trusses to more easily align the truss and wall framing. These trusses carry only half the load of the others and will be sheathed with plywood or OSB at any rate.
None of us are as smart as all of us.