Quote Originally Posted by johnfrwhipple View Post
Kerdi is a recommended method of waterproofing.

Drywall is not permitted in wet zones. You might apply Kerdi over the backsplash near your sink or behind your stove but not in your shower.

In Europe Kerdi DS is used for primary wet zones (showers) and steam applications. Kerdi is used elsewhere.

Many liquid membranes also list drywall as an acceptable substrate but you would be equally outside of industry standards if used in a shower.

Best thing to do is to phone the TTMAC or purchase their specification guide. Drywall is listed only in non-wet zones.

This is really just common sense and Jim you site the proper rules when you choose. I would imagine you have a specification guide handy. Why not open it up?

Question... why would it matter? Lets for a minute leave Kerdi and all of its "problems" out of the picture. And lets have an answer that isn't just about "approved uses," but an actual rational thinking answer.

If your showers are so perfectly waterproof, who gives a crap if there's drywall behind it? It's only function is to provide a stable surface to attach the waterproofing to. Drywall is an acceptable substrate for backsplashes and other tile applications, so reason would state that it would be a sufficient substrate for a shower, if it was water tight. I thought your waterproofing was perfect, so the drywall behind a waterproof shower would actually be the best place to install it, as everywhere else, its exposed to a higher level of moisture and has a higher chance of becoming a mold problem.

That said, I'm not advocating it as a substrate behind anything that it is not specified as acceptable by the manufacturer. Kerdi specifies it as an acceptable backing. It is not acceptable to use as a tile backer w/o waterproofing in a shower, which would be a "wet zone"... can't tell you how many times I've seen that... "Ceramic tile is waterproof, right?"