new bathtub/shower combo has no floor support - additional info

Old 12-20-07, 08:29 AM
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new bathtub/shower combo has no floor support - additional info

I received 2 replies to my below posting - unfortunately, the builder of my new home (keep in mind that this is WV, and there are no codes to speak of) was not a licensed contractor; there is no real warranty and he was relieved of the job, due to other issues, prior to the home being finished. Bottom line: he will not be back to correct this problem. I was in hopes that I could fix it myself with some type of expanding foam or other cushioning agent. Anyone got any ideas?
ORIGINAL POSTING: My new homes master bath tub enclosure has no support under the tub, between it and the sub-flooring, other than one 2-by-4 board set close to and parallel with the tub wall-side of the enclosure. When we step into the tub and move around, the tub often makes a popping or cracking noise, and I worry that the lack of support underneath will eventually lead to a fracture of the tub floor. The tub enclosure backs up to the open wall joists above the inside steps leading down to the basement of the house, so I can access the back of the tub and view the underneath. Is there any type of expanding foam or other support material that I can inject under the tub to give it support?
Old 12-20-07, 08:49 AM
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shower support

Hi Nancy

First, you should use the reply button to keep all your posts in the same thread. No Biggie

Yes, I have known many plumbers that used foam to support the bottom in between the built-in cross supports of acrylic showers and tubs. I would slide 2 x 6 and/or plywood under the center of the tub, or under the built in cross supports (as needed) to take most of the load.

You'll want to use a spray foam like "great stuff" and work from the furthest point out. Do it in stages so you can gauge the required amount after expansion. This stuff will expand for quite a while depending on temp. No using the tub until the foam completely sets up, read the can instructions.

Do not use the window and door foam, it will not harden and stays flexible. Also, do not use the triple expanding foam, it is not as dense as the regular stuff.

Hope this helps, good luck
Best in 2008
Old 12-20-07, 09:54 AM
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The manufacturer's installation instructions will usually include a diagram of the required support.

With the tub moving around like that the drain/overflow may have loosened, make sure it's tight.

However you support the tub, make sure that you provide access to service the DWV and supply plumbing. If this is a hydro-therapy tub, the manufacturer will specify the minimum required access, remember that that's a minimum.

Also, considering the quality of the rest of the work, if it is a HM tub I would recommend you have an electrician check to insure that the required GFCI protection is present and that pump and heater if present are on appropriate sized circuits, dedicated if required by the manufacturer or the NEC.


If this bathroom is typical of the quality of the rest of the home, and it has never been inspected, you might want to have a experienced home inspector go through it with you and come up with a prioritized punch-list of required work to help you get things under control at minimum expense.

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