Truss Installation
We are going to be installing our roof trusses soon. I just have a few questions about proper install.
We are going to build a 1ft ladder overhang at the gable ends. Should I start my 24oc truss layout from this point 12in out? Do I need to account for the fascia board and add an extra 1in to the 12in and start my layout from there? I might be overthinking this, but if I started my truss layout from the end of the overhang, none of the trusses would fall over every other stud which are 16oc. I do have a double top plate but I still thought trusses needed to fall over every other stud.
Next question is. What is the best way to attach the gable end truss to the top plate? Toe nails? Brackets? Timber locks? We will have sheathing extending down from the truss to the end wall but I don’t want to rely on just that to hold it in place.
Thanks in advance!
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
Unless your roof is very large and you have a fairly heavy snow load, you don't have to land trusses over studs. It looks good but I have only had to upgrade from a double top plate once, with trusses that had a 44' span and a 50 psf snow load. Even then it was just barely necessary, to make the engineer happy.
Structurally it doesn't matter if your starting truss is less than layout from your gable end. In fact, structurally the first truss could be twice the normal layout, but nobody does that. If you place the first truss closer to the gable end you will need to buy another truss, which would probably cost more than having a bit more plywood offcuts, but it depends on the roof.
Cottagebuilder,
I've never seen a layout that didn't start off the gable truss. That's what the truss supplier will expect, and their drawing show. One advantage of lining up trusses and the wall studs below is that it simplifies plumbing, ducts, and electrical runs. The only layouts I don''t do that way when framing are floor joists. Those I often space from the middle so I don't end up with very small cavities against the rim-joists, making insulating and air-sealing easier.
I sheath gable trusses when they are lying flat on the top plates, leaving a 3/4" plywood overhang on the bottom to nail to the upper top plate. Before standing the truss I run a 2"x6" the length of the top plate set in 1 1/2". This provides backing for the ceiling drywall, and backing to nail off the bottom chord of the gable truss to. Depending on where you are (high wind or seismic area) you may need additional hardware to attach the truss to the walls.