Water resistant drywall?

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Fruitfilledevil

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Remodeling a standard tub/shower.
Can I use water resistant drywall with red guard or aqua defense membrane for water proofing? If not, why? I've redone a stand-up shower using sheet rock and aqua defense membrane but the drywall would be easier to work with. As long as the waterproofing membrane is good, what does it matter what's behind it? Tiles are 4x16. I was looking at kerdi-board, but it's very expensive. Thank you.
 

wwhitney

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"Moisture resistant" drywall is basically of no benefit over regular drywall, it doesn't provide any significant additional resistance to bulk water. Maybe it provides a little more resistance to high humidity conditions.

As to the suitable substrates for your waterproofing, you need to check with the manufacturer as to what they've tested it on and had approved. Kerdi has been tested and approved on drywall, IIRC. Not sure if any of the liquid applied waterproofings have been tested on drywall.

Goboard is one less expensive alternative to Kerdiboard. And Kerdi over drywall is cheaper materials-wise than Kerdiboard, although it requires more labor.

Cheers, Wayne
 

John Gayewski

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There are several layers of defense in a shower, mainly because of time. Time is the one thing most people don't consider. The reason not to use drywall is because it's not water resistant. Whatever waterproofing you have will breakdown over time or be penetrated by vapor/water over time.

You want something resistant to water. Things move. Expand, contract, repeat. I don't like cement board because it cracks.
 

Jadnashua

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If the makers of RedGard or AquaDefense, or similar products thought it would work and pass any tests in wet areas over drywall (any type), they'd recommend it. Code does not allow drywall in a wet area for a reason. Only two (that I know of) companies have done the testing and gotten approvals for the use of drywall in a wet/shower area: Schluter with Kerdi and Laticrete with their Hydroban (sheet, not the liquid).

Personally, I'd probably use KerdiBoard, or Kerdi, or maybe WediBoard above a tub/shower.
 

Nmarolf

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I've used a product called Denshield. I think this is what you are looking for. Sold at the usual DIY stores. It cuts like drywall and is inexpensive. Tape and thinset the seems (100 silicone in between boards) and redgard them if you want. Has a waterproof membrane on one side.
 
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