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The problem: My house has a Hip Roof. The trusses have been nailed to the interior walls. The result is truss lift. Because all interior walls are attached, the interior wall weight is lifted from the floors, causing noisy floors during the winter. I think I can overcome this by screwing the sub floor to their joists when the flooring is renewed. However, at the side of the house, where the hip roof is at right angles to the main trusses, there is a truss with a 2" x 8" top beam, running in the same direction as the main trusses, that the small side (hip) trusses connect to. There are two openings (a doorway and an arch) under this hip section. They are attached at right angles to the exterior walls. Again, these trusses are nailed to the interior walls. When truss lift occurs, the exterior attached side of the openings stay fixed but the interior side gets pulled up, causing the drywall to crack at the top interior side of the opening. What I think is happening, is that the 2" x 8" beam is exerting greater lift than the other trusses, causing the cracks.
Question: is it safe to remove the nails attaching these side hip trusses to the interior walls? enter image description here

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Yes, I would definitely disconnect roof trusses from the top plate of interior non-bearing walls. In fact truss manufacturers require it.

When bottom chords of trusses rest on top plates it puts the bottom chord in “double bending” and the trusses are not designed for that kind of stress. In fact truss manufacturers recommend a clip that fastens to the top of the top plate and to the side of the bottom chord. This clip has an oblong hole where it attaches to the bottom chord so the truss can move up and down. The clip also keeps the truss from laying over on its side when fully loaded.

If you decide to remove the nails I’d install one of these clips that the manufacturer recommends or at least install a couple of nails on each side of the bottom chord so it can’t move laterally. Here’s an example clip:

enter image description here

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  • "truss manufacturers require it" -- what exactly does this mean? To me, "requiring" something implies having some leverage to enforce it. Do you mean, e.g., that the manufacturer will deny warranty coverage if the trusses were improperly connected? – nanoman Jun 21 at 4:54
  • @nanoman Yes, it’s in there instructions for installation. – Lee Sam Jun 21 at 6:45

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