I just bought a house built around 2006. The floor has a ~32' span supported by 24" deep trusses on 19.2" centers. The trusses do not have strongback bracing installed (well there is a 2×4 nailed face down into the bottom chord, but that doesn't count). As a result there is some bounce when you go across it at a brisk walk. I plan to install 2 strongbacks at ~10' spacing. My question is how can I get the strongbacks into place? I have had a couple of thoughts but am unsure which one will provide the best performance. Trusses are a standard 24" truss web with no HVAC openings
-
Remove some siding and cut a hole in the rimboard and run the longest 2x6s I can get, and affix them to the verticals. Patch and seal the rimboard, patch and seal the wrap, replace siding and done.
-
Run ~6' ~2×6 sections up into the truss from the inside, lap them between trusses on the inside with a 19.2" 2×6, then run long (8' probably) 6" sections of more flexible OSB along the other side of the vertical to reinforce the connection (?) screwing it into the laps and the verticals.
Anyone dealt with this situation and have any thoughts?
Best Answer
I've built quite a few homes with floor trusses, and we didn't always have the foresight or opportunity to lay in strongbacks during the truss set. Have you tried getting longer 2x6 boards in there? You might be surprised how much they flex. I'd bet you can get 16-footers in there without much issue.
I'd start with that. Just don't let your grip slip and smack yourself in the chin. Once you have one in place, use it up against the top chords as a slider for the next ones.
Otherwise, you're onto something with the OSB. As you probably know, OSB is what makes up the vertical component of TJI joists, meaning it has plenty of strength on that axis to act as a strongback. You could rip 8-10" widths from 1/2"x8' sheets, flex them into place, and stagger the butt joints of two layers by two trusses. I have confidence that this would do at least as well as 2x6 lumber.
Actually, 7/16"x10' OSB is commonly available. If you shortened them to 115.2" you'd span one more joist.
FYI, such strongbacks are usually set against the top chord. By keeping them tight in all cases you ensure a flat floor. (Even engineered trusses can have some crown or wiggle to them.) If you have the option I'd move your ducts down and do that. It might help to have them temporarily out of the way anyway. Otherwise it probably doesn't matter much at this point.