I’ve had some disagreement with a truss salesman about the best way to handle trusses where they intersect non-bearing partition walls. I always nail trusses to the interior wall with 60d pole barn nails, or else put diamond shaped tie-down fasteners on. This way when truss uplift occurs, the whole wall is lifted, preventing the wall to ceiling drywall joint from cracking. I know there are ways for drywallers to prevent this while leaving the trusses free, but I don’t know the drywallers (I’m a framing sub) and I’d rather know that I’ve taken care of the issue before it’s ever an issue. Also, I’ve always done it this way and people I’ve worked for in the past have done it this way. A nice side benefit is that it cuts down on the number of rat runs I have to nail in since the wall acts as the bottom chord bracing.
Truss guy says I shouldn’t fasten trusses to walls. He says it’s bad, unacceptable, not to be done, blah, blah, blah, but he can’t tell me why.
So, is truss guy spouting a line he heard somewhere along the way (he’s not an engineer) or am I missing something important here?
Replies
I,m only a plumber so you can take my opinion and do with it what ever you like but more than likely the trusses are not engineered to support the weight of the hanging wall if truss lift does occur?
Maybe Boss Hog would wade in and enlighten us on this subject with more authoritative information. But just for fun I will give it a bash.
My guess is that the truss should not be held down anywhere except the designed locations, usually the exterior walls. As the truss ages and cycles in and out moisture the center can lift. If the center was held down by the walls closer to the center it might load the truss in the same way as if several thousand pounds had been placed on top of it. This would be in addition to any, planned, loads such as snow or wind. The combination could exceed the design load of the truss and damage it.
I do know that there are metal reinforcements, made for this situation, that are nailed firmly to any intermediate walls but are fastened to the truss by way of a vertical slot with a nail that slides along it. This is designed to reinforces the wall laterally but allow the truss to float vertically.
Your truss salesman is right.
If the trusses decide to lift up, they're gonna take the wall with them. Trouble is, they might not lift up evenly. If one truss lifts up more than the next, you could end up with some nasty drywall cracks. (I've been out on a house where this happened in a big way)
Or you might end up with doors that don't open and close, if one side comes up and the other one doesn't.
What if the whole wall lifts up? What's gonna happen at the bottom of the wall, and the trim? Or will the top plates pull loose from the studs? Something's gotta give. And it could be expensive to fix once it's happened.
The clips 4LORN1 mentions are the way to go. If you prep the framing right, you can't take responsibility for the drywall. If you're concerned about it, talk to the GC and tell him your concerns. It's up to him to specify how the drywall is installed.
KC makes the point that the trusses could be damaged from the excess weight added to them by nailing them down. This is theoretically true, but I don't know of a case where that's actually happened. It really doesn't concern me a whole lot.
BTW - Lack of attic ventilation is the worst culprit in truss uplift, IMHO. But that's another subject...........
The forest would be silent if the only birds who sang were the ones who sang the best.
Simpson makes a connector for this application,check out their catalogue
http://www.strongtie.com/products/connectors_list/STC.html
By all means use the Simpson clip or similar to brace the walls to the truss chords, while still allowing truss uplift and not lifting the wall. Re the drywall, I recall a how-to article in JLC or FH that discussed this, and showed how to hold gypboard fastening back from such a joint so as to allow the truss to lift, flex the ceiling board, but not stress and break the tape joint at the wall / ceiling juncture.
Use the simpson clips. If the truss goes up and takes the wall with it, the nails that were holding the wall down start sounding like a cricket symphony. Any step near the wall makes all kinds of racket. I've seen that noise with it lifting as little as an 1/8th of an inch.
When you drywall the ceiling don't screw within a foot of the perpendicular wall this will let the drywall flex with the truss.
Good information and thanks to all who responded. Those simpson clips are easier than the diamond clips and still take care of the rat run issue. The only question that comes to mind then is what to do at walls that run parallel to the trusses. Do I still put a drywall backer block on or should the rockers be using drywall clips? And more importantly, what about parallel walls that are closer than 16 inches to the nearest truss? If there's only 5 inches from wall to truss, that drywall will be under pretty substantial stress if the trusses move a whole lot.
I'm not disagreeing with anyone, just wondering what the best way to handle it is.
Thanks.
I would use clips and on any truss `12 inches or closer to a parallel wall omit the screws and let the wall drywall hold up that end.
Download this .PDF documanet - It shoes the proper way to do walls with trusses running parallel.
http://www.woodtruss.com/images/publication_images/ttbpartsep.pdfI only date stewardesses. Or maybe it just seems that way. Women always seem to be showing me the exits.
Nice reference. Thanks.