Tiling over Kerdi and over drywall

kntryhumanAugust 16, 2009

We put "blue board" or green drywall in the shower and around the tubs.

I'm putting Kerdi in the shower. Can I put the Kerdi directly over the green board or do I have to put cement board first?

Can I tile directly over the drywall around the tubs or do I have to put cement board first?

Thanks for the help.

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Avanti Tile & Stone

Kerdi seems to work best over standard drywall. You need to use a GOOD unmodified morter.... Cement board really isn't needed, although some pros still use it. Make sure to wet it THOROUGHLY if you do. Kerdi is totally waterproof, which is why standard drywall is fine, according to Schluter. I don't like using greenboard as it's only about two spits better than drywall and had some kinda wax that makes Kerdi more difficult to adhere to.

    Bookmark   August 16, 2009 at 10:21PM
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You can Kerdi over the drywall, it need to go a minimum of 72" above the drain or above the shower arm, whichever is greater.

In the tub if you're not using Kerdi, you can't tile directly to any paper-faced drywall, whether it be green, blue, or any other color. That's been against code since '06. If you have drywall around the tub, then you can pull it and replace it with cement backer board or some other approved backer board. It's best to NOT install cement board over drywall.

I agree with lazarususa that the properties that make greenboard moisture resistant can have an effect, but thinset still sticks to it fine.

Outside of a shower or tub surround you can tile over drywall with no worries.

    Bookmark   August 17, 2009 at 5:31PM
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