I have a fiberglass bathtub in my mobile home that is roughly 5' x 4' in size. The mobile home is a 1978 doublewide, and the tub was in the home when we purchased it, 5 years ago, so I'm sure it's very old.

There is a creaking in the tub that has gotten much worse over time. When you walk around in the tub, you can feel more give in some areas and the creaking is horrible. We do not have the money to replace the tub.

I have a small access panel in the adjoining closet, and I took a picture (attached) that shows the underside of the tub. I liked the idea of spraying foam underneath the tub, but as you can see from the picture, it is very far off the ground and there are drain pipes that are under one part of the tub.

Click photo for full size
bathtub picture

3 Answers 3


It's not a great picture, but it looks like the tub is supported by wood and foam. It's possible that the wood has rotted, or the structure that supports the wood has rotted or been compromised in some way.

You can spray foam under there wildly, if you want. But if the structure that will support the foam (and tub) is compromised, it's not going to do you much good.

You're going to want to get better access, and evaluate the structure. The answer may be as simple as adding a few extra braces, or as complex as ripping it all out and replacing it. Without a better look, it's impossible to say for sure.

Since this is a mobile home, it's not likely this is a botched installation. Instead it's likely due to age, wear and tear, and/or rot.


You can combine spray foam (to get the fit) with block foam (to take up most of the space) if you can get block foam in place from the access hole.

Or you can use lots of spray foam - but give each application of it time, as it can swell more than you think if you apply a large amount at once.

If you have to get at the pipes you're probably already in "rip the whole thing out" mode. But you could try to clear those with rigid foam and only spray between the top of the rigid and the bottom of the tub.

Partially fill the tub with water when foaming, to weight it down a bit.

  • Thank you very much! I found a second access hole towards the front of the tub, and I see that when they installed it, they framed in a rectangle with boards on the ground and then set the tub on a layer of styrafoam. Is this common practice?
    – Jenni
    Aug 2, 2015 at 21:54
  • I can try to get the spray foam under the styrafoam under the tub also to help add more support.
    – Jenni
    Aug 2, 2015 at 21:55
  • @Jenni downside to spraying the foam in there is that if it doesn't solve the problem now you have a bunch of foam in the way of a fix that works.
    – jqning
    Jan 3, 2016 at 0:44
  • @jqning - Which would be what, exactly? This answer used to have an upvote. The only problem I see is, as mentioned, the bulging of the tub walls, if you're over zealous while applicating the foam.
    – Mazura
    May 3, 2016 at 4:16

Most of these types of tubs sit in thinset. If you put in Styrofoam, foam or anything like that it will degrade over time and your tub will be noisy and will flex on you. I am really surprised you aren't having major flexing issues.

The tub doesn't need to be replaced, it just needs to sit on something more stab that will form to it - why thinset is used a lot.

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