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Community and Q&A

Light load bearing foam

rstagl | Posted in General Questions on

I had remodeled our first floor master bath and installed a new shower base and walls. I did glue down the base posts but something has become loose and there is movement in floor and lots of squeaks when moving around base. I hate to tear out new walls to re-install base.
I have access to under floor from Basement and have cut some holes to access and tried putting in spacers to support base but it seems to have made it worse. I would like to know if there is a spray foam spray that would handle the weight of a person and base and not allow movement downward that causes the squeaks. I would close up the openings I made and there is still access  under base with the opening made in floor for the drain. Frustrated an hoping someone has an easy fix  for this. Thank you

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  1. GBA Editor
    Brian Pontolilo | | #1

    Hi Rstagl.

    I have never done this myself, but I have heard of people injecting canned spray foam beneath squeaky tubs to stiffen them up. First, I would make sure that it is the shower base that is flexing and squeaking and not the framing and subfloor, though.

    I would imagine that the foam you choose (a low-expansion foam vs. a highly expanding big gap filler) would depend on how how much space there is to fill, and the ease of access.

    This is going to make it a bit more difficult to pull the base when remodeling because polyurethane foam is a strong adhesive, but you generally have the recip saw out for that work anyway.

    I bet some other GBA members will have some thoughts on this and maybe some techniques to share.

  2. Expert Member
    NICK KEENAN | | #2

    Many shower and tub manufacturers recommend foam used this way. I would first check the installation instructions and see if they have a recommendation.

  3. Expert Member

    Be careful. I've had a tub lift when I used too much foam underneath. Trying to compensate by standing in it did nothing.

    1. Expert Member
      BILL WICHERS | | #6

      Maybe it would be possible to fill the tub with water while injecting the foam? The tub will Wright a LOT more full of water, and hopefully have less chance of lifting due to foam expansion.


  4. Expert Member
    Michael Maines | | #4

    I'll second Malcolm's warning, because I've had the same thing happen. With low-expansion foam and a light touch you should be ok. Mortar used to be the recommended filler, and some manufacturers still recommend it. Hard to get it into place after installation, though.

  5. rstagl | | #5

    Thanks for the update. I was leaning on spraying closed cell expansion foam. I do have room to spread it around and I especially appreciate the warning on using low expansion foam and avoid it lifting base. Didnt even consider that being a problem, figured it would come out by drain area as that opening is pretty large, around 7- 8" Dia
    Could anyone suggest a foam brand best for this kind of application? least compression over time
    Again , Thanks guys, I'm new to this forum.

  6. 730d | | #7

    Canned foam should work well. Use less than you imagine is needed. I had great success for years setting whirlpools and tub or shower bases down into a full bucket or box of all purpose taping mud. Put a piece of poly on top of mud if you are concerned about it adhering to the base.

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