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  1. #1
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    Help needed: Oil Canning noise prevention, floor joists rubbing on return/ducts

    Having reoccurring issues, last two sets of homes that we've built have had oil canning noises.

    had to cut open the floors in a dozen places to stuff insulation between the joist and the return air, or some other duct. Someone walking on the open web joist, with 3/4in OSB, would cause in some cases, the joists to rub against the duct below. And cause the creaking/groaning noise.

    Driving me nuts, some cases can only be heard in the dead of the night. So I'm walking through jobs at 6am or 7pm across all floors to find and mark noises.. and every time its a duct.

    I switched joist suppliers, and hvac contractors. Internet says this is a common issue, and is one for our new home warranty program.

    Is there a way to run returns not tight against the joists? or some material people put between during install?

  2. #2
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    I have probably been at 15,000 homes with the trunk lines tight against the floor joists and can't say I have heard of this. Little creaks when the ducts expand and contract occasionally but not what you are explaining. Unless there is a headroom problem there should be no reason that the trunks can't be hung a 1/2" or so below the joists aside from a bit more time installing.

    Wonders about these joists that seem to e bowing....

  3. #3
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    Quote Originally Posted by Glennhvac View Post
    I have probably been at 15,000 homes with the trunk lines tight against the floor joists and can't say I have heard of this. Little creaks when the ducts expand and contract occasionally but not what you are explaining. Unless there is a headroom problem there should be no reason that the trunks can't be hung a 1/2" or so below the joists aside from a bit more time installing.

    Wonders about these joists that seem to e bowing....
    Last guy who I gave the job to assured me he is experienced with this and always hangs his stuff half inch below. I just did 12 repairs on two houses and it was all tight.

    The houses you're usually in, open Web joists or?

    Based on various Web searches it seems like a common issue. Which I guess is understandable with any bit of deflection from the joists.

  4. #4
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    The houses you're usually in, open Web joists or?

    Probably 90% no. I'll have to look next time I see open joists and see how they are run. My last house had TJI spans about 45 feet but I don't recall any noises. Can't remember. Sounds like you found your solution. Actually You may be able to just lower those existing trunks 1/4" or so with no problem.

  5. #5
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    Sounds like a static issue to me

  6. #6
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    Quote Originally Posted by Glennhvac View Post
    The houses you're usually in, open Web joists or?

    Probably 90% no. I'll have to look next time I see open joists and see how they are run. My last house had TJI spans about 45 feet but I don't recall any noises. Can't remember. Sounds like you found your solution. Actually You may be able to just lower those existing trunks 1/4" or so with no problem.
    No solution, the putz who said he wouldn't run them tight.. Ran them tight.

    Last four guys I've talked to said they run them tight. So I'm wondering if it's common for people to leave a gap between the joists, and any technical reason not to?

  7. #7
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    There is no reason they can not be hung lower aside from the extra time it takes and any loss of headroom. It may be easy to blow off the time factor in your mind but trust me, it does take a good bit more time measuring and hanging ducts below the joist as opposed to tight especially if only one guy is running them.
    Quote Originally Posted by Garuda889 View Post
    No solution, the putz who said he wouldn't run them tight.. Ran them tight.

    Last four guys I've talked to said they run them tight. So I'm wondering if it's common for people to leave a gap between the joists, and any technical reason not to?

  8. #8
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    Quote Originally Posted by lkapigian View Post
    Sounds like a static issue to me

    No, forget he said oil canning. It's not that.

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  10. #9
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    use 24 g metal and be sure the sections are cross braked.

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  12. #10
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    Quote Originally Posted by timjimbob View Post
    use 24 g metal and be sure the sections are cross braked.
    How would that stop groaning from joist deflection into the metal?

  13. #11
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    "How would that stop groaning from joist deflection into the metal? "

    I don't see that it is the HVAC contractor's problem, blame the carpenter for deflecting joists. This is where the general contractor job is for. A good GC verifies ssytems are working together and anticipates problems

  14. #12
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    Quote Originally Posted by timjimbob View Post
    A good GC verifies ssytems are working together and anticipates problems
    Hence my thread looking for assistance. I don't want this issue on future jobs. Thanks for your help.

  15. #13
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    Not trying to be an A55 but going forward, If you believe the cause is from duct rubbing on the joists, I would think the solution/fix is pretty simple.

    As the general you are selecting and paying the sub-contractors. You place in the specification/contract/PO however you award the work to the HVAC contractor that the HVAC ducts must not be touching the floor joist (1/4", 1/2"). The penalty is they either repair to meet the requirement or they pay for the cost of the repair to stop the noise.

    As the general don't you or your site foreman inspect the sub contractor work after they are done? If the duct is touching they don't get paid as simple as that

    On new residential contruction jobs I walk the house when we are done just to listen for noises and adjustment that may be needed.

    Once the house get loaded with furniture (deadweight gets added) noises show up that were not found during the final walk through at turnover. As for me I install duct tight to joist if possible, but I also install a flex boot between the furnace plenum and main trunk.

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