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Can you attach a Clevis hanger to the subfloor?

Synbio
Synbio Member Posts: 17
in Strictly Steam
I have a black iron steam pipe that runs between floor joists, and thus, under the subfloor. The pipe is rubbing against a different perpendicular beam underneath it, so I want to raise the pipe slightly. The easiest option would be to use a Clevis hanger attached the subfloor and raise the pipe slightly so it stops rubbing against the beam and causing extra noise.

Can you attach a Clevis hanger to the subfloor or does it not have enough strength?

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 24,557
    That would depend on what the subfloor is made of and how thick it is. If it is the typical 5/8 or 3/4 inch modern plywood construction, I would say no unless your hanger has a pad base to attach and multiple locations for screws, A number 10 screw in such material can only support 50 pounds -- assuming the plywood is in good shape.

    A better option would be to span between two joists with a substantial, properly hung, 2 x 4 or 2 x 6 and support the clevis from that.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Mad Dog_2
  • Chris_L
    Chris_L Member Posts: 336
    I agree with @Jamie Hall that it depends on what the subfloor is made of, but if the subfloor went in when the steam pipes did, it almost certainly is not plywood.

    I did exactly what you are asking about five years ago to take out a dip in a pipe. I had to put a lot of tension in the hanger to do so. The subfloor is 3/4" planks, and this hanger has held fine for five years now:

  • Jamie Hall
    Jamie Hall Member Posts: 24,557
    Good dense softwood planks are a different matter -- 100 plus pounds per screw is fine.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Synbio
    Synbio Member Posts: 17
    That looks awesome @Chris_L can I also ask what is that padding between the pipe and hanger, is that a piece of rubber?
  • Chris_L
    Chris_L Member Posts: 336
    @Synbio, that is a piece of plastic milk carton. Not sure it was really necessary, but I figured it couldn't hurt to help prevent expansion and contraction noise, as it does for radiator feet.
    CLambPC7060
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 9,157
    edited November 2023
    Good job @Chris_L. If however you had the plywood or OSB for the subfloor I would suggest that you support with the hanger upside down. Then add a 2x4 or 2x6 to the bottom of the floor joists in order to push the pipe up from the bottom.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    offdutytechSynbio
  • mattmia2
    mattmia2 Member Posts: 10,754
    You can also get a hanger for threaded rod that screws in to the side of a joist or beam if that would work for you.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 16,283
    What @ChrisJ did is fine . But I would have used 3" screws and don't walk upstairs barefoot. LOL In most cases a 3/4 or 1" screw won't poke through if it does you will know.

    You can also add multiple hangers if you doubt the screw holding ability of the sub floor or do as @EdTheHeaterMan posted.

    Unistrut (not seen much in residential) across the bottom of the joists or between the joists will work as well

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