Floor joist in the way

Discussion in 'Shower & bathtub Forum & Blog' started by daisyk77, Jun 8, 2007.

  1. daisyk77

    daisyk77 New Member

    Messages:
    3
    Location:
    CT
    I'm installing a cast iron tub in a 1930,s home. The rough dimension for the drain is 14 1/2" on center. I have a floor joist @ 15". Do I have to sister the joist and cut th old one out? Will that even give me enough room?

    Thanks!
  2. leejosepho

    leejosepho DIY scratch-pad engineer

    Tub drains I have seen do not need much vertical room directly below the actual hole in the bottom of the tub. Once through the floor, the drain usually then runs horizontally to meet the overflow pipe coming down from the end of the tub. You should be able to cut through the floor and notch the top of your joist just enough to install the drain without greatly compromising the strength of the joist ... and if you have only 2X6 or 2X8 joists, you can first add plates on the sides at the bottom.

    My own clearance problem was at the point where the drain and overflow come together, and here is how I did (with sistered 2X6s) what I am suggesting you might be able to do:

    Attached Files:

    Last edited: Jun 9, 2007
  3. daisyk77

    daisyk77 New Member

    Messages:
    3
    Location:
    CT
    Thanks, Unfortnately my floor joist run vertically not horizontally, so is notching still an option without ruining the integrity of the joist?
  4. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    You may need to put in headers to support the ends of the cut joist and reinforce the joists that the headers are attached to. The joist hangers that are available at HD and Lowes make the job neater and stronger.

    Then you can span the distance between the headers with one or two offset joists that give you clearance for the plumbing.

    If you are sistering a joist you need to run the "sister" at least 3 feet beyond the cut on each end so the joint will take the bending load.

    You need to get kiln dried lumber for work like that. If you put in wet lumber it will shrink while the old stuff doesn't and you will have local sags in the floor.
  5. leejosepho

    leejosepho DIY scratch-pad engineer

    I do not understand what you mean there. From your initial description, I am assuming your joists run perpendicular or "crossways" to the length of your tub, as do my own, and that you have a joist directly beneath the tub's drain opening. Is that accurate? Maybe I have misunderstood. Also, I am presently talking *only* about the actual drain connection at the tub, and not about how you might continue your plumbing on from there to wherever it has to go.
  6. Terry

    Terry Administrator Staff Member

    Messages:
    15,048
    Location:
    Bothell, Washington
    So where is the p-trap on the tub drain pictured above?

    [​IMG]
    Last edited: Jun 2, 2010
  7. daisyk77

    daisyk77 New Member

    Messages:
    3
    Location:
    CT
    Thanks, Leejosepho- The floor joist splits the tub in half the long way not perpendicular. Sorry for the confusion
  8. leejosepho

    leejosepho DIY scratch-pad engineer

    Right here:

    Attached Files:

  9. leejosepho

    leejosepho DIY scratch-pad engineer

    It still might be possible to use notches to get the drain and overflow together and connected to a drain line -- a little "creative plumbing", so to speak -- but I do not know how many elbows would be considered acceptable in such an arrangement. Bob has well described the "boxing" that is common, and that can work fine as long as all factors are considered.
  10. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    That is a running trap is is not allowed / code.

    Where is the vent?
  11. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,684
    Location:
    Cave Creek, Arizona
    drain

    Leejoseph. You seem to have a love affair with square vent 90's in a drain system. I hope you never have to have it snaked because it is going to be a real chore to get the snake around those square corners and then remove the stoppage. Depending on the drain you are using, most can be installed next to the joist and the drain pipe angled to meet it and the overflow riser offset to connect to the tub opening.
  12. leejosepho

    leejosepho DIY scratch-pad engineer

    What is the issue?

    The tub drain-line is essentially "self-venting" in the sense that it is physically impossible for any amount of water capable of draining from the tub to siphon the trap or build up enough speed to run right on through. I had the same kind of "engineering dilemma" with the drain line for our washing machine quite some time ago, and the same configuration first used there also works perfectly.

    No, I actually do not, and I studied/pondered all my known options for that particular tub drain for a very long time before finally doing what I did.

    Same here! But, there will definitely be an easy-access panel in that wall when I finally get it finished.

    Is there a "kit" for an offset overflow, or is that something that must be fabricated? This is the first I have ever heard of doing that, and I really would prefer some better plumbing there. My concern is that the drain line might eventually plug up from "stuff" that did not wash on through hanging around inside and drying out on the wall of the pipe. If I could get the trap under the tub -- 2X6 joists is the next problem -- putting a vent in the wall just a half-tub-width away would not be a problem.
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