# styrofoam bottom on bathtubs



## joecaption (Nov 30, 2011)

If thin set would crumble why would it be used under tile backer and under tile?


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## jackwashere (May 5, 2010)

joecaption said:


> If thin set would crumble why would it be used under tile backer and under tile?


I want to use it under styrofoam under a bathtub. Will it crumble over time as people get in/out of the bathtub?


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## gregzoll (Dec 25, 2006)

Use Self Leveler under the space that you are placing the tub. Once you place the tub in there, while it is still wet, it is not going anywhere. The other option is to use a thin layer of Great Foam, and then set the tub in it, before it sets up, and be done with it.

Other option is to place some 1/8"-1/4" plywood shims under the tub to even out. My guess is that they placed the Joists Crown down in that area, or the house foundation settled in that area. How old is this house, and can you post some pictures from below the bath and the bath area, showing what you are dealing with.


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## jackwashere (May 5, 2010)

gregzoll said:


> The other option is to use a thin layer of Great Foam


You mean Great Stuff?

That's an idea! $4 bucks. It would bond well with styrofoam and work its way in under the tub.


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## TheEplumber (Jul 20, 2010)

jackwashere said:


> You mean Great Stuff?
> 
> That's an idea! $4 bucks. It would bond well with styrofoam and work its way in under the tub.


Be careful it doesn't expand and lift your tub.....


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## joecaption (Nov 30, 2011)

It expands to much and will compress when stood on. Not a great idea to use foam.


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## gregzoll (Dec 25, 2006)

joecaption said:


> It expands to much and will compress when stood on. Not a great idea to use foam.


Not really, depending on which version you use. No different then the foam block that is underneath the tub attached to it.


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## jackwashere (May 5, 2010)

joecaption said:


> It expands to much and will compress when stood on. Not a great idea to use foam.


Good point. Foam gets spongy. Styrofoam is hard and different than Great Stuff and other similar foams. Thanks for the suggestion however.

I think I'll just install backer board onto the plywood and apply a layer of self leveler or thinset (the other option you mentioned) on it then rest the tub on that. I will have to raise the cradle by 1/2" to compensate for the 1/2" backer board. It seems like the best safest option.


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## djlandkpl (Jan 29, 2013)

You can get hardibacker in 1/4. It will save you from raising the whole tub. Raising the whole tub may impact your floor and how it meets the tub.


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## plummen (Jan 10, 2010)

Mix up some plaster and trowel it out where the tub will be sitting


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## Davejss (May 14, 2012)

plummen said:


> Mix up some plaster and trowel it out where the tub will be sitting


Yup. That's the way its been done for the last ......years.


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