Having previously suspended a plumb bob from the bottom chord of my garage truss, and having observed its !/2″ or so movement up and down in the dead of winter (IL), I now want to build an interior wall under this 22′ truss and have been advised to place compression foam between the truss and top wall plate. Question is, is the bottom chord in its lowest ebb now or highest?? as it is freezing, covered with snow, and doesn’t seem to be fluctuating much now. Also, is it a function of temperature such that this summer it will move up or down? Thanks for any help!
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You are expirencing truss uplift. There are truss clips that allow for fastening the truss to the partition wall and still allow for its upward movement.
Assuming a level floor, build the partition wall the same same height as the exterior walls and attach the clips to the trusses.
FWIW, typicaly the trusses will be at their lowest point in the warmer monthes.
Terry
While they make some brackets that allow movement, 1/2" is a fair amount and you will potentiall run into problems e.g. w/ drywall finish. Maybe you'll have to attache wall top trim to the ceiling and allow it to float on the wall to keep a gap covered? This may be a source of air leakage, too.
The other post gives you a hint. Check level from the ext wall top plate. I'd think that would tell you if the chord is now up or down.
Trusses usually rise a bit in the winter, so they should be about as high as they're gonna get now.
But - A 22' truss shouldn't have much movement in it.
Do you have a ceiling in the garage already? If you do, how much ventilation is there?