# 2 Drywall boards behind shower tiles?



## Termite (Apr 13, 2008)

There should not be drywall behind shower walls. It is a poor practice that crumby builders employ, and is now illegal by code. Instead of re-installing drywall, you should install 1/2" thick cement backerboard. It comes in 3x5' sheets and is screwed to the wall. Much better substrate for tile. Since tile/grout is nowhere near waterproof, the backerboard needs to be waterproofed with an application of RedGuard, Kerdi, or a similar product before tile is applied.

As for removal of tiles from the floor...Hopefully there's a cement mud bed under the tile, as well as a drain membrane to direct water to the drain. Whether or not you'll be able to remove the tiles without compomising either will be luck of the draw.


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## Termite (Apr 13, 2008)

One layer of 1/2" cement board is the norm, so you don't need two layers.

Had the tiles been properly installed, you'd have never got them to come off. Be sure to use dry mix thinset, not mastic, when you apply the new tiles. Mastic is baaaaad in wet areas.


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## Confused1 (Sep 15, 2008)

Thanks for the great info!

Here is where I'm currently at. I don't know what I got myself into but I'm definitely hoping to do this on my own.

http://img169.imageshack.us/my.php?image=img0163fp5.jpg
http://img247.imageshack.us/my.php?image=img0164ei9.jpg
http://img515.imageshack.us/my.php?image=img0165sv4.jpg

In the pic from my first post you see 2 rows of tile still there at the bottom center. In http://img169.imageshack.us/my.php?image=img0163fp5.jpg
there was a cement behind it, almost like a cement wall. It was about 1 1/2" thick and runs all the way down in between the flooring and the wall. I went ahead and took most of it out.

http://img247.imageshack.us/my.php?image=img0164ei9.jpg shows how far up the tiles went. They didn't take it all the way up to the ceiling, which is what I want to do. The red dashes show where I want to cut the drywall for replacement with the cement boards. I'd rather just replace the areas I need rather then that whole side of the bathroom.

As far as the installation of the flooring goes, anything I need to know about that? When I took the tiles off, there was nothing underneath except for the, I'm guessing that's the cement mud bed your talking about. 

I think (I hope) taking everything down is the hardest part. Once I get all the material together, it should be smooth sailing.


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## Termite (Apr 13, 2008)

OK. Don't get excited to hang tile just yet. The devil's in the details and the prep work! Hang your backerboard with "rock on" brand or similar backerboard screws. I'd put a screw every 6-8" in every single stud. Once you hang your dura-rock or wonderboard (or similar) cement backerboard on the walls where you'll be tiling, you'll need to mud and tape the seams. The tape is mesh fiberglass tape specifically for backerboard, and the mud is dry mix thinset. This unifies the joints. If you don't do it, you're guaranteed it will crack your grout joints near the seams. It doesn't have to look good, it is purely for function. Use a putty knife to mud the joint with thinset mixed to a peanut butter consistency, bed the tape in the mud, add a bit more mud to cover it up, and smooth it out. It takes 10 minutes or less.

Not knowing exactly what is going on in the floor scares me. If the mud bed appears to be solid go ahead and re-use it. However, I strongly recommend that you use the Kerdi system by Schluter since you don't know what sort of membrane, if any, is under there. Kerdi will also take care of waterproofing the walls. It isn't cheap, but is absolutely the best system there is for tile showers, and it is pretty much foolproof. It will also make the transition from floor to walls watertight. Youtube has plenty of videos on this stuff I'm sure.


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## Termite (Apr 13, 2008)

To answer your question about the floor, it is simply set in thinset mortar. Be sure it pitches toward the drain, which I'm assuming it does. 

Don't use the pre-mixed thinset. Buy HIGH QUALITY thinset, not cheapo stuff. It does make a difference.


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## Confused1 (Sep 15, 2008)

I wonder if I can just break down the floor mix / mud bed down to the sub floor and just start fresh, new liner and all. Like you said, its a mystery whether or not there is anything under there. I figure if I've went this far, I might as well go the extra steps and make sure its done right. Besides, everything looks kind of rotten and aged. Not sure what would be the most effective way of doing that but I'm guessing chisel out piece by piece. 

Also, http://www.youtube.com/watch?v=JNB8bs5VYoI&feature=related gives a really good perspective on the steps of what to do.

And BIG thanks for all your help so far!


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## Confused1 (Sep 15, 2008)

Ok I'm about ready to put it all together but one last question. The flooring is cement and not wood. When I apply the material (in this case, roofing paper), I'm assuming I will be using an adhesive of some type instead of stapling. Is there anything you recommend I use as far as the adhesive goes? Or anything to just keep it from moving


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## Termite (Apr 13, 2008)

The flooring? Are we talking about the bathroom floor or the shower pan floor? 

If it is the bathroom floor, and the substrate is cement (not cement backerboard...an actual slab), take a look at Ditra. Good way to put tile over concrete.


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## Confused1 (Sep 15, 2008)

Ok almost there! Now where the backerboard meets the floor, I read that I leave .25" space there. Is that for the tiling to slide in there? Or am I supposed to fill that gap up?


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## RippySkippy (Feb 9, 2007)

thekctermite said:


> There should not be drywall behind shower walls. It is a poor practice that crumby builders employ, and is now illegal by code. Instead of re-installing drywall...the backerboard needs to be waterproofed with an application of RedGuard, Kerdi...


Just for clarification if someone is considering Kerdi, it does go over standard drywall in a shower...NOT cement board. If one uses Kerdi, it should be applied with a high quality, un-modified thin set.


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## Confused1 (Sep 15, 2008)

Where the cement board meets the drywall ceiling, what do I do there? I'm going to tile the wall all the way up to the ceiling but I'm not sure if I just use thinset to fill the gap or what.


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## Big Bob (Jul 27, 2007)

Confused1,,, My new handle is confused 2...

did you replace the shower pan?:huh: your post 9/17
tar paper? old liners looked like that. and older liners were made of lead.


odds are you will need to cut your tile as you meet the ceiling..
cute tricks are to plan a border below and make two even rows to the top.

If you did not replace the pan while wide open... buy extra floor and wall tile and save or buy more grout...(to go 3 or 4 high at base perimeter) if you bought and installed sanitary base ...buy more ...bull nose ..cap etc.

or risk a patch job in the near future.

Now is or was the time to replace the shower pan.


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## dgustin (Feb 1, 2010)

*There should not be drywall behind shower walls. It is now illegal by code?*

I noticed in the thread that drywall behind showers is illegal by code and I was wondering if anyone would please direct me to where the code states this specific issue. I am having an issue with really shoddy workmanship and they are telling me that the code does not specify that drywall is illegal.

Any help would be greatly apprecited by "thekctermite" or anyone else who might have information on this matter.

Thank you


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## dgustin (Feb 1, 2010)

thekctermite said:


> There should not be drywall behind shower walls. It is a poor practice that crumby builders employ, and is now illegal by code. Instead of re-installing drywall, you should install 1/2" thick cement backerboard. It comes in 3x5' sheets and is screwed to the wall. Much better substrate for tile. Since tile/grout is nowhere near waterproof, the backerboard needs to be waterproofed with an application of RedGuard, Kerdi, or a similar product before tile is applied.
> 
> As for removal of tiles from the floor...Hopefully there's a cement mud bed under the tile, as well as a drain membrane to direct water to the drain. Whether or not you'll be able to remove the tiles without compomising either will be luck of the draw.


I noticed in the thread that drywall behind showers is illegal by code and I was wondering if anyone would please direct me to where the code states this specific issue. I am having an issue with really shoddy workmanship and they are telling me that the code does not specify that drywall is illegal.

Any help would be greatly apprecited by "thekctermite" or anyone else who might have information on this matter.

Thank you


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## Limit54 (Nov 6, 2009)

I don't know all the codes but in this case logically it just makes sense. Imagine drywall screwed to studs and moisture and water and mold setting in. What will hapopen? Well, it will weaken and eventually fail. Now if you add tiles to the mix you are adding weight to the drywall and as the drywall weakens from water and moisture ect.. it's going to start to crack and eventually fall. In most cases you would be able to punch the tiles and the wall would crumble. I'm not sure how long this would take but in any case it wont be too long before you are replaing the drywall and tiles with cementboard and new tile.

Get them to do it right the first time.

They also might have used greenboard(drywall that has a green finish on one side) This is by no means waterproof. The manufacturer states that it is water and moisture resistant BIG DIFFERENCE!! I see a lot of people using this for showers and this could pose a major problem in the future.

I actually have one of my basement showers lined with greenbaord and then a plastic shower over that. I checked the greenboard and it seems to be ok but it is not in direct contact with water. 

This was not my work and it is comming down very soon but it is an interesting real life test for me. I'm just wondering how teh humidity is affecting it??

I'll find out when it comes down.


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