View Full Version : Is tile on mold-resistent drywall a bad idea?

06-12-2007, 10:10 AM
We were originally planning to install a fiberglass surround so we installed mold resistent drywall but then decided to tile it. Is it a bad idea to install tile on this surface?

Is there something that I can seal it with so that water will not be a problem with it?


06-12-2007, 10:21 AM
Not that I know of, but you would be wise to replace at least the board that will contact the tub with cement board.

06-12-2007, 12:30 PM
I assume this is around a tub...

Check out www.schluter.com (http://www.schluter.com) and look at Kerdi for shower systems. Then, look at Dilex. The problem with drywall is it doesn't like to get wet. If you use the Kerdi and install it per their diagrams, you end up with the drywall totally waterproofed. Using Dilex lets you get away without having to use any caulk. You need to look at the Dilex info to see how to make a tub waterproof at the tub/wall interface using the Kerdi, but the Kerdi info tells you about the membrane itself. This is what I've got on my tub surround. I also used it to build a shower for my mother over Christmas. For more help and assistance, check out www.johnbridge.com (http://www.johnbridge.com). You don't have to use the Dilex, but if you do, you'll never have to add or replace caulk.

06-12-2007, 05:43 PM
tub-shower? Shower here? Then NO you cannot tile drywall or greenboard; it must have waterproofing first.

Redgard, Mapei, Wedi, Kerdi, whatever.


06-13-2007, 07:38 AM
Yes, this is around a tub.

The drywall that I used says...

Mold & Water Resistent 1/2" GP DENS ARMOR PLUS

Anyone know anything about this stuff?

Thanks for the info jadnashua, I'll take a look.

06-13-2007, 09:06 AM
sorry, if it's just a tub, then you don't need any "protection". Any substrate under tile is fine. Any substrate.


06-13-2007, 07:26 PM
Doh, no I'm sorry. Responded to quick. This is a standars tub and shower.

06-14-2007, 04:12 AM
In my opionion you would be best off to replace the current board with concrete board. Green board is no longer allowed in some areas where I am located because of the problems with tiles coming loose after years of use. Keep in mind that the whole idea of installing tile to board is to get the mortor that the tile is to be bonded to to become one with the wall board. Why take shortcuts----go with the best! Concrete board!

06-14-2007, 06:19 AM
... Is there something that I can seal it with so that water will not be a problem with it? Plastic sheet underneath Cement Backer Unit (CBU) cement board. Make the plastic longer than the CBU so it hangs lower, so water drips down into the tub's tiling flange. Cut the CBU so short that it leaves a little strip of air (a gap) behind the last row of tiles at the bottom instead of allowing it to touch the tub.

You have asked the right question, at the right time. :D

To help you to confirm this in your mind, search on key words mold, greenboard, "paper facing" (both words together with quotes). You will see that no mold resistant product can resist mold for long. The term is not helpful to owners, builders, occupants; it helps sales, not safety.

If you want to leave the product on the walls, you can add Kerdi on top. Or Wedi. Or Redgard or Mapei. This will make your space smaller by 1/4" - 1/2" so factor that in when you tile.