Shower Stall Tiled Wall Question

[DKAudio]

I'm helping a friend redo his bathroom. The shower stall already had a nice concrete pan & drain. He doesn't want to touch that since it already can receive tile, has a nice slope, drain works, etc. He framed out the shower and on the walls he used 1/2" exterior grade plywood. Normally I would tell him to use heavy roofing tar paper and 1/2" Durock on top of that. However, my concern is how would I make a water path with the existing concrete pan? I know you should caulk all angled joints but if water gets in the grout and starts working its way into the corners I'd be worried it would sit since there is no barrier there to get it into the pan.

[HayZee518]

drip edge

my guess is you can use a beaded edge tile bullnose upside down. quickset it in place and when dry use regular grout in the spaces.

[HayZee518]

tile edge

I just looked and another edge finish is called a V groove or angled cap.

[pushkins]

You do not want a drip edge !!!!!! The whole point of a shower stall is to direct the water to flow towards the drain and NOT have any place it can get caught.
The wall material should go down into the floor pan cement. Inside this cement there should be a rubber liner that runs up the wall behind ANY wall materials.
Mud pans/cement pans are designed to absorb moisture when it does and they ALL do the water soaks into the cement bed until it hits the rubber membrane, then it is guided to the drain's weepholes.

I'm assuming that since you made no mention of seeing any rubber membrane sticking out anywhere that it doesn't exist, if this is the case then I hate to be the bearer of bad news, but it's going to leak, no if's or buts it's going to !

I'm also assuming that as it's a cement pan (and you made mention of durorock) that the floor and walls will be tiled .....is this the case ?

[DKAudio]

You do not want a drip edge !!!!!! The whole point of a shower stall is to direct the water to flow towards the drain and NOT have any place it can get caught.
The wall material should go down into the floor pan cement. Inside this cement there should be a rubber liner that runs up the wall behind ANY wall materials.
Mud pans/cement pans are designed to absorb moisture when it does and they ALL do the water soaks into the cement bed until it hits the rubber membrane, then it is guided to the drain's weepholes.

I'm assuming that since you made no mention of seeing any rubber membrane sticking out anywhere that it doesn't exist, if this is the case then I hate to be the bearer of bad news, but it's going to leak, no if's or buts it's going to !

I'm also assuming that as it's a cement pan (and you made mention of durorock) that the floor and walls will be tiled .....is this the case ?

Yes, the walls and floor of the shower will be tiled. I did not see what the old shower stall looked like before he redid the walls. I also do not see any rubber membrane under the cement pan though, I believe they made that pan directly on top of the concrete slab, the concrete pan has been there for decades.

[pushkins]

Been there for decades ? then it may just have a layer of felt paper between the pan and the concrete slab. Or one in the layers of the pan bed.

Installing ply as a wall structure won't work I'll try to list the reasons:

1. It's not water proof, exterior ply will absorb all the water it can it just doesn't rot, but it will transfer the moisture to anything it touches like studs.

2. Tile most certainly won't like staying glued to ply, especially where water is a constant issue.

3. There is no way to seal the joint between ply wall and cement pan.

Have to remember wood and cement expand and contract at very different levels, assume you can get a tile to hold long term to the wood, what happens when the wood moves through normal expansion and contraction......the tile at the bottom will separate it's grout line from the pan tile, now there is a gap and it's right where there is a gap between the wall and pan.

Typically speaking the wall panels (backer board) are cemented into one of the pan layers with the rubber membrane behind the wall panel, this is a crucial water proofing step.

[DKAudio]

Been there for decades ? then it may just have a layer of felt paper between the pan and the concrete slab. Or one in the layers of the pan bed.

Installing ply as a wall structure won't work I'll try to list the reasons:

1. It's not water proof, exterior ply will absorb all the water it can it just doesn't rot, but it will transfer the moisture to anything it touches like studs.

2. Tile most certainly won't like staying glued to ply, especially where water is a constant issue.

3. There is no way to seal the joint between ply wall and cement pan.

Have to remember wood and cement expand and contract at very different levels, assume you can get a tile to hold long term to the wood, what happens when the wood moves through normal expansion and contraction......the tile at the bottom will separate it's grout line from the pan tile, now there is a gap and it's right where there is a gap between the wall and pan.

Typically speaking the wall panels (backer board) are cemented into one of the pan layers with the rubber membrane behind the wall panel, this is a crucial water proofing step.

Yes, I realize that, I would never tile to ply in a shower stall! Remember, I am walking into this project trying to save it. Like I said in my first post, I plan to use a heavy tar paper stapled to the ply and ½” Durock on top of that (at the very least I would use Ditra on the floor and Kerdi on the walls, assuming they don’t flex). My concern is how to create a water path from the new ½” Durock to the existing concrete pan on the slab.