Retile over shower greenboard?

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Old 02-15-08, 07:30 PM
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Retile over shower greenboard?

I set out to do a simple re-caulk in my shower and quickly discovered there were bigger problems. My dilemma now is that I've pulled a few tiles off the wall to see how bad the problem is, and now I really don't know the answer.

House is 9 years old, and we've been in it a year. My guess is this shower hasn't been touched at all since new construction.

I noticed chronic mold problems on the caulk around the shower base after the first couple months in the house. After getting down there and scrubbing it once or twice I noticed it looked like a crappy caulk job, and a few of the bottom row tiles had cracks in the grout. So tonight I started trying to scrape out the old caulk, and as I did I ended up pulling out big chunks of grout with it. Pictures show the story better than I can tell it, so here are a few.

http://www.carhack.org/downloads/IMG_0221.jpg
http://www.carhack.org/downloads/IMG_0220.jpg
http://www.carhack.org/downloads/IMG_0222.jpg
http://www.carhack.org/downloads/IMG_0223.jpg
http://www.carhack.org/downloads/IMG_0224.jpg

If you look at that first one you can see the situation. The shower base feels like a hard plastic. The wall tiles come down and leave about 1/4" gap between their bottom and the edge of the shower base. That gap was filled with grout, and then mostly caulked over. But when removing the caulk I found that it was applied extremely thinly, and in many places it didn't actually cover the grout. There were numerous cracks in the grout, so I ended up stripping out both the caulk and the grout along the bottom. In the process I noticed some loose tiles, and as big chunks of the grout came out I noticed there was a lot of moisture behind them.

So I pulled off a couple of the loose tiles and found a lot of dark mold behind them, but what concerned me more was that the drywall (greenrock I think) was very damp, moldy, and in a number of spots the paper just came right off with the tiles exposing the gypsum.

As you can see in the pictures, the nail heads are pretty rusty. To my surprise the studs, which you can see in a couple of the pictures, don't appear to be water damaged at all. I poked and prodded with a screwdriver and they appear to be in perfect condition. You can also see some type of insulation in there. The walls behind the shower tiles are internal walls, with conditioned space on the other side. But it's all on the 2nd floor above the garage, so I'm not really sure just how conditioned the space between the walls is.

So my problem is that my simple caulking job has turned into a bigger job than I expected. But how big? Can I just dry the whole area out real good, re-glue the tiles to the green rock, grout it, caulk it, and be done with it? I would think that no matter how well I grout I'm still going to get water seepage through to the greenrock. How big a problem is that? I know it's not an ideal backing, but is it viable?

Only other solution I can think of is pull the whole thing out and replace the green rock with cement board or something more waterproof. That's a much bigger job than I'd attempt myself.

Should I be concerned there's no water barrier between the shower and the wall studs? Or the insulation? There's no evidence of water ever getting to them. It looks like all I got was a bit of seepage through the grout that wicked up the gaps between the tiles and the drywall and molded.

Thanks for any thoughts or advice.
 
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Old 02-15-08, 10:30 PM
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That substrate is unsuitable. You are getting water past the tile and your wallboard is absorbing it, so, if you seal the area under where you have lost tile, the water will get in beside it. You really need to deal with this or you will continue to get mold growth, which can be unhealthy. Kill mold with bleach, the industrial strength concentrate you get at a hardware store is better than household bleach.

You can pull the bottom 12" of tile (3 rows or so) all the way around, and allow the wallboard to dry thoroughly. Following that, fill the gap with mortar, then apply at least two coats of 'Redguard' or some other waterproof membrane that you can trowel or brush on. Then reset the tile.

If that seems like too much work, you could use some kind of acrylic or vinyl surround that you adhere to the existing tile wall.
 
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Old 02-16-08, 07:40 AM
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OMG, tile on drywall inside a shower......

Honestly, the entire wall needs to come down, tile and all. There should have been a cement board installed for the tile, and not a drywall/greenboard.

Greenboard is not acceptable for use within a shower.

Shower should be like:

Plastic moisture barrier attached to studs-
Cement board instead of drywall
tape and tile

or

Cement board-
Apply RedGuard
tile
 
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Old 02-16-08, 08:53 AM
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Yup, she's a goner! No hope for that one and no need to kick it around here. Take it apart and start over.
 
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Old 02-17-08, 09:36 PM
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Thanks for the quick replies guys. And thanks for the advice. The more tiles I pulled off the more wet moldy drywall I found. After pulling off the greenrock I found that the studs were damp and moldy behind it. I guess I shouldn't be surprised at all.

What really surprises me is how many sites out there give shower/bath construction advice that's exactly how my shower was constructed before. Bare studs, then drywall/greenwall, then tiles. Found some "how-to's" on the "This Old House" site, HGTV, and a handfull of different tile and tub manufacturer sites that all showed this as recommended construction.

For my reconstruction I'm leaving the same shower base and studs in place. I'm figuring on 4 mil poly layer on the studs, then hardibacker, then thinset and tile. I'm planning on the hardibacker stopping about 1/2" above the shower base, the poly hanging inside the top edge of the base, and the tiles coming down to about 1/4 from the flat part of the shower base.

When I grout and caulk, my plan is no grout on the wall to wall corners or the wall to base edge. Those just get caulked. Anything wrong with this plan?

I've read a lot of people doing a layer of greenboard, then cement board, then the tiles. I can't really do that without having to redo the studs or finding a new base that would fit the specific layout.
 
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Old 02-18-08, 08:12 AM
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Your plan sounds good. There's alot of DIY type of sites for installing tile, and the majority of them are wrong. We have some good people on this site to help you through the process if you need more help.

No need at all to install greenboard anywhere in a shower except the ceiling if it's not going to be tiled.

I personally would use a 6mil plastic instead of 4, but 4 should work alright too.
 
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Old 02-18-08, 08:32 AM
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Your basic plan is good. You will find that as you go along there will be a lot of details to be resolved. Dont guess at them. Come back here and ask. The only stupid question is the one you didnt ask.

How old is that shower base unit and what condition is it in. If its old and your not sure how much longer it will last, know is the time to do something about it.
 
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Old 05-18-08, 08:51 AM
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Do I Remove Cement Board with Residual Grout Before Re-Tiling?

Re-doing tile on bath room floor. There is an ~1" cement board that, when the tile was removed, has residual grout/mortar with the tile striations.

Question: Can I successfully re-tile over this as a substrate, or do I have to pull cement board up and start over.

Also, what should be basic sequence for each. For instance, if I pull up cement board, do I add plastic, is there a better product than cement board out there. Thanks.

- Bob for Bob & Dawn
 
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Old 05-18-08, 09:03 AM
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bathroom fix

Definitely need to pull out drywall, but also make sure you clean and moldy areas with a water (2/3) and bleach (1/3) solution and let it dry well before proceeding. You'll be glad you did it right -- once it's all over!
 
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Old 05-18-08, 10:47 AM
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Allison, posters said he has cement board, not drywall.

Bob,

I've never seen 1" cement board. You probably have a mud wall. Grind down any high spots and inspect the substrate for any cracks or defects. If it looks ok, install tile back over it.

If you want to tear it out, do this:

Install a 6mil plastic barrier against studs

Install 1/2" hardibacker over barrier and studs

Install seam tape as you install tile.

What does your shower floor consist of?
 
 

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