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fiberglass shower stall

Posted: Mon Sep 02, 2013 12:45 pm
by boom271
In my house there is a 32 inch x 32 inch one piece fiberglass shower stall already installed. The floor of the shower bends a little when you stand on it. I opened up one of the walls of the shower from outside of the shower, and I can see there is about one inch of unsupported space between the floor of the shower and the plywood sub flooring. Only the outside edges of the shower stall are supported. I want to fill in the unsupported space so the floor of the shower no longer bends (or cracks in the future). What kind of material should I put in the space? Would wood shims, or a can of gap filler that you spray in , or gravel or sand, or mortar work? The space I have to get to the unsupported area in tight, since the shower stall is already installed and only one wall is easily accessible.

Thanks for any help you could provide me.


Re: fiverglass shower stall

Posted: Mon Sep 02, 2013 3:24 pm
by Shannon
It is best if you could spray in some spray foam, but it will be difficult to get it completely in there with the space you have to work. If it looks like there is a wooden sheet layer embedded into the fiberglass bottom of the shower then usually they do not require extra support but you could place a few wood shims under the base where you can reach. Placing only shims in a few spots on a shower that does not have a wood support can cause to much pressure and more cracking. If you can spray foam under it try to get as much area sprayed as possible. You may achieve this better by adding small hose or drinking straws to the existing straw that comes with the can. I add drinking straws by using electrical tape to hold them in place. Be careful how much foam you put under it some have lots of pressure, you may want to use a low expansion foam usually used on windows.

Re: fiberglass shower stall

Posted: Sat Nov 16, 2013 5:22 am
by maturediyer
I am taking out my old bathtub and replacing it with a one piece fiberglass shower, I have a lip on the front of my shower and want to cut it off if i can to lower it for my disabled wife so how do i fix the floor for it to sit on...i was thinking 2x4"s laid flat should be a good enough base but will it work. She is a large woman so i dont want it bowing anywhere in there from her weight. I am in a mobile home a 2005.


Re: fiberglass shower stall

Posted: Sat Nov 16, 2013 7:52 am
by Shannon
You could also lay down a bed of mortar about 1/2" thicker than you think you need then lay a sheet of poly over that and then install the shower base. Press the base into the mortar until you have it to where you want it and it is level. This should completely support the base .