[timgwen]

Please help. I've spent hours online and cannot find my particular problem.
I'm adding a shower to current bathtub with tile 30 inches up the wall. I've removed the drywall on the upper tier above the tile to install cement board. I've also removed the upper row of tile on the lower tier to make sure the appropraite backer board was installed. Indeed there was cement board behind it.
My problem is I don't see any indication that there was a vapor barrier installed on the lower half. I REALLY didn't want to remove the tile on the lower half. I'm hoping to simply continue the tile up the rest of the wall.
So my question is: Do I vapor barrier half the wall or do i need to remove the lower half? How do i know they didn't put some type of sealant over the cement board already?


Gwen

 

[timgwen]

I guess I'm having a hard time communicating my problem.
There is existing cement board and tile on the bottom 3 feet of my tub surround. I already tore out the upper 3 feet of drywall and installed cement board. My problem is, I cannot tell if there is moisture barrier on the lower half (existing) tiled wall. I'm not sure how to tell or what to look for. I was going to redgard the upper half but what good would that do if the previous installer did not waterproof the lower half? I hope that makes more sense........

 

[Blondesense]

Can you post a couple of pics?

First let me say I've done a lot of research here and other places, and I retiled my own shower, but I am far from an expert.

There are a couple of ways this is usually done. One is a plastic or something similar behind the cement board. If this was done you should be able to see it since you removed the top drywall. The other way is a roll or brush on membrane. It is usually a distinct color so when applying it you are sure to get full coverage. If this was used you should see some indication of it in the area where you removed tile. When I did my shower the stuff I used was blue, but it could be red or some other color depending on the product.

The thing that slightly concerns me is the fact you were able to get a row of tiles off. If the tile was done correctly using a thinset on cement board I would think it would be difficult if not impossible to get them off without destroying the CBU. I would be concerned that a mastic or some other adhesive was used that is not a good choice for a shower.

Again, pics would help here. But in your shoes, if I had any doubts I would tear the whole thing out and make sure it was done right.

Edited to add: Actually, I would be surprised if you did find a moisture or vapor barrier. Since it was built as a tub only, a vapor barrier would be an unnecessary and added expense for a builder.

 

[timgwen]

So I decided to play it safe and remove the lower half of tile and then waterproof the cement board if it is good enough shape.

You are right......the tile is coming off very easily almost leaving a completely clean wall board!

CX told me that they may have used mastic since it was just a bath surround. The requirements are not near as strict for a bath only installation?

Anyway, I think I can reuse this cement board......what do you think?

 

[Blondesense]

The requirements are not near as strict for a bath only installation?

Correct. A tub surround just has to withstand an occasional splash. Tile will pretty much do the job. A shower, OTOH has water hitting it directly on a daily basis working its way through the grout and tile into the wall. You need something to really stop the water.

As far as reusing the CBU, I'm gonna leave that question to someone else. How clean is clean? And how does the CBU meet the tub flange? Again, pics would help.