Truss uplift and drywall concerns
While researching the various practices/approaches to building inner non-load bearing walls in a building using roof trusses (which is my proposed build) I ran across concerns/issues with drywall damage (mostly, it sounds like, tape separation) from trusses lifting up: https://explore.trim-tex.com/content/truss-uplift-solutions I learned that there are clips that are used to help mitigate this problem,. BUT, that’s for a conventional build. What would one do if building with a dropped ceiling? I’m planning on a dropped ceiling to run ventilation tubes, wiring and such (in conjunction with some chases).
As of now I’m leaning toward Intello Plus as the air barrier attached to the underside of the bottom truss chords, followed by furring strips (perhaps 1/2″) and then attaching 2x4s on edge under and parallel to the truss chords. Drywall and inner wall framing will attach to these 2x4s: attachment of wall framing will depend on orientation- attach to blocking perhaps. So…
Is this a case of a solution (not yet defined) looking for a problem or if this is a real concern/issue how would I mitigate?
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Mark, it's not always a problem, but when it is a problem, it can be a big one. On one of my past projects I did not provide documentation on how to deal with uplift to a truss with a 42' span and now the kitchen, at the center of the house and with cabinets that run to the ceiling, have a 1/2" gap in winter. The way it's detailed, it's still airtight, but unsightly (and as a designer, embarrassing.) So please learn from my mistake and plan for it.
Here's a good overview with solutions: https://www.buildingscience.com/documents/reports/rr-0107-drywall-wood-and-truss-uplift/view.
Here's another: https://www.jlconline.com/how-to/interiors/truss-uplift-solutions
Michael, many thanks for the input.
I'm currently trying to figure if I couldn't use those slotted anchor braces to connect my dropped ceiling (faux) joists to the trusses' lower chords. In essence it would float the ceiling, allowing the trusses to flex. A problem I could see here is whether the 2x4 faux joists could hold up the drywall while keeping deflection to a minimum (deflection that would cancel out and then exceed say a 1/4" to 1/2" slot travel). I'll see if I can scribble something up that would better show what I have in mind. NOTE: the trusses will be elevated above the top plate (and interior non-load bearing walls); this will allow the ends of the faux joists to (on edge) to rest on the top plate with a gap above to the trusses' lower chords.
Mark, you could definitely keep the ceiling joists independent from the trusses. Table R802.4(1) shows allowable ceiling joist spans, which is basically what you have: https://codes.iccsafe.org/content/IRC2015/chapter-8-roof-ceiling-construction#IRC2015_Pt03_Ch08_SecR802.4. You could connect the ceiling joists to the trusses to reduce the span but keep the center portion of the trusses free to move.