Partition Separation Lag Bolting
Is lag bolting the bottom chord of a truss to the top plate of a wall a proper fix to correct truss arching, assuming the attic is properly vented?
We, as an industry, do not suggest attaching the bottom chord of a truss to the partition wall as a proper preventative measure against truss arching. This will not prevent the truss from arching in response to the moisture content differential between the top and bottom chords. In some cases, the attachment of bottom chord to the partition wall has lifted the entire wall assembly as the truss arches.
I have read a lot of information on partition separation. Nothing so far has discussed the subject as it applies to nonbearing walls with scissor trusses. I have scissor trusses in my bedroom and I would like to add non-bearing walls for a closet in the room. Do the same techniques apply to the scissor truss as a common truss? I'm thinking of the deflection of the scissor truss and how it will affect my drywall.
You are probably well aware of the mechanisms of partition separation. If you are not experiencing it in the rest of your house, it would be safe to assume that it will not occur in the portion with scissor trusses. If it is a big concern, you may want to consider employing the floating drywall corner details as described in SBCA’s Partition Separation document.
What may be of more concern is the scissor truss movement you mention or horizontal deflection. This is the tendency of all vaulted framing to thrust outwards. The key decision you’ll need to make is whether the potential vertical or horizontal movement is of more concern. You can't allow for both unless the top of the wall remains completely unattached; in that scenario, the wall would not affect the truss but the top of the wall would be left laterally unstable.