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Community and Q&A

Is this truss lift??

Robert Post S.E. Pennsylvania Zone 4a | Posted in GBA Pro Help on

The link is to images of this case. Click the “show info” upper right of slide show for captions.

This production house in S.E. Pa. has a trussed roof. It is 3 years old. The first season (October) a drywall joint opened up (1/4″ +/-) at the change of ceiling plane in the picture where the flat ceiling meets the “cathedral” ceiling. The builder installed a foux beam over that area to conceal what they thought would be a seasonal event. Now the next joint over opens up seasonally.

This crack is located less that 24″ from a lam- beam and parallel to it as well. Two different trusses come together right at this beam.

What do you think?

Many thanks!

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Replies

  1. Foster Lyons | | #1

    Robert,
    I don't think it's truss lift. I think it's just expansion/contraction combined with an unfortunately long drywall joint.

    I don't see any separation between the ceiling and the interior walls (photos 7864 and 7866) which is what I would expect to see with truss lift. Also, the open crack is quite wide. In that location, lift might cause a crack but I wouln't expect it to be so wide.
    Foster

  2. Michael Chandler | | #2

    I agree with Foster in that it's not classic truss lift which occurs at interior walls rather than in the run of a ceiling but it is very similar to the type of separation I've seen at the ridge in scissor truss roofs. it reminds me of a saying we have down here in North Cakalaki "the proof of a builder isn't in how few mistakes he makes, but how little they slow him down" just get in there and add another layer of drywall glued and screwed over the original layer with joints staggered well beyond the crack and transfer that flaw to hiding behind the faux beam where it should have stayed to begin with. Odds are good that the faux beam is trapping the drywall leading to the movement of the seasonal expansion to the new location. I'm seeing the bottom chord of the trusses in some of those photos - a 2x6? what's the R-value up there? Does this builder still have a "right to repair" or are we into deep animosity and legal action already?

  3. John Brooks | | #3

    Robert, did you notice the gap (see attachment)
    It is possible that the bottom chord is shrinking....and the top chord is expanding
    have you seen :
    http://www.buildingscience.com/documents/insights/bsi-023-wood-is-good-but-strange?searchterm=truss+uplift

  4. Robert Post S.E. Pennsylvania Zone 4a | | #4

    Foster- there is separation at an adjacent wall/ceiling joint, about 8' long.

    Michael- Yes, possibly 2x6. The insulation was moved for the pictures. the r-value is approximately 40. The owners are philosophical and no animosity or legal action. They have lost confidence that the builder can solve this and just want a final solution after 3 years.

    John- yes, I've read that. The reason I posted this is because it did not appear to be what was described in the building science article. That gap is the end of the truss for the cathedral ceiling. I suspect there is some movement like that but would not necessary expect that kind of joint separation so close to the end. But I don't know.

  5. Robert Post S.E. Pennsylvania Zone 4a | | #5

    I like the over-laid drywall approach. Of course we'd have to run down the hall with it. How much confidence would you have in this solution given the fact that we are starting out with a gap that moves from 0-3/8" at spots?

  6. John Brooks | | #6

    "owner says they did not attach the drywall to the beam" ... I wonder how he knows that?

  7. Robert Post S.E. Pennsylvania Zone 4a | | #7

    John- the owner is an engineer and has learned a lot through this process. He was there the last time they attempted to remedy this (which included removing much drywall in that area) and instructed them not to attach to the beam. He says they didn't and that's what I have to go by. It was a good call. Maybe they did and that is part of the problem.

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