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Thread: Fiberglass tub is starting to flex

  1. #1

    Default Fiberglass tub is starting to flex

    I have a one piece fiberglass tub/shower. I just noticed when I took a bath the other day that it was flexing when I moved. I thought it was going to crack or something. I did a little investigating and noticed that the tub has a support that runs the length of the tub on both sides. However, I don't think there is any support in the center. I went to ********* and they suggested a spray some expanding foam underneath the base. Last night I opened up the access panel to the hot and cold valves and tried to see if I could see under the tub. There appears to be a reinforcing brace across the width, but does not make contact with the floor (about an inch clearance). I proceeded to spray the foam under the base using a 5 foot piece of plastic tubing. The problem is I can't see how much foam is being released. Therefore, I can't see how much the foam has expanded. Do I just keep sparaying foam underneath everyday until the flexing stops or do I just call a plumber. I'm a big guy about 240 so I'm very concerned. I a take a shower it flexes but it does not sound like its going to crack. Any suggestion would be very appreciated.


  2. #2
    DIY scratch-pad engineer leejosepho's Avatar
    Join Date
    Nov 2006
    200 miles south of Little Rock


    You definitely need(ed) to do something there, and I suspect the foam was not the best idea. The bottom of a tub needs a solid foundation, and that foam is easy to crush.

    I would stop spraying foam and find a way to get something solid under your tub before its bottom cracks through altogether. That happened to me a couple of years ago, and I ended up cutting out the bad part and glassing in a new bottom. The work you need to do (or to have done) might be difficult, but the alternative is the complete replacement of a bottomless tub.

  3. #3
    DIY Junior Member wes-in-nc's Avatar
    Join Date
    Jan 2007
    Hickory, NC.


    I think your tub should have been set in motar when it was installed for support. Its gives it a solid feel when your in it. I agree that the foam will only crush under your body weight. Is the access panel your only means of access?


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