Shower niche - not waterproof because of gap

Apologies as I realized I posted this on the plumbing forum and not the bath/shower forum.

I will repost in the correct forum.


Hi all,

My name is Karen and I am new to the world of bathroom remodeling. I would really appreciate your help with the following problem.

We have had our GK put in shower niches in our shower/tub combo (we are gutting bathrooms, just not moving any plumbing around). I read up on waterproofing and saw we should have a waterproofing membrane like redgard, so we asked them to do that including on the niche. There is hardiebacker on the walls and then redgard on top of it.

The problem with one niche is that when we examined it it wasn't properly built. They used hardie to build it out, but the corners arent aligned, and one part of the niche doesnt have hardie on it. There are gaps in the corner that would clearly lead to water leaking into the walls or at the least have moisture exposure. The other niches were built properly, but not this one. You can see the plywood beneath.

They had already tiled all the walls around the niche and the back wall of the niche. I don't think it is an option to have them take the tile out and redo the niche entirely, so my question to you is, given the situation, what is the best way to minimize water leakage? When I raised the issue to them they said they would take care of it - and then they put cement on top of one of the gaps to fill the gap (not sure if that is waterproof and rather doubt it), then some redgard on top. Doesnt look as tho the Redgard is applied well either.

I am really worried about water damage and there are still some gaps on the top left and right corners of the niche. What do you recommend I ask them to do to fix this? Use a waterproof tape to tape off the gaps? Does cementing it work? Obviously the best thing would be to have them redo the niche entirely, but tile is already on the wall around it and not sure if they can just pull out surrounding tile. It hasn't been grouted, just set.

I am at my wits end trying to figure this out and know it has to be fixed now or we will be facing the possibility of water damage down the road. Any advice would be most appreciated. Thank you.

From your description I am completely at a loss as to what it looks like. Is it a tiled niche, and if so there should not be "gaps" in the tile or grout. Is the tile thinset or glued on?

It is a tiled niche and I will post a picture shortly so that you can see. The tile is thinset on, but hasn't yet been grouted.

Attachment 17452Attachment 17453

Sorry, I misspoke, the niche is only partially tiled (just the back board of it). The sides of it are not. The gaps are not in the tile but rather, in the corners where the hardiebacker should all meet.

I"m not sure if the pictures are large enough, so let me know if they are not. Hopefully it's a little clearer. I've taken a close of of the top left hand part of the niche, where you see the ceiling of the niche doesn't meet the side (and the ceiling is not hardiebackered). There was already a gap in another corner of the niche, which gap they covered with cement and redgarded, which I would be fine with if I knew that that was a good waterproofing method.......

Well, a couple of things - tile will not survive applied on dimmensional wood - it can on ply, but not in a wet area. There won't be much water on the top of a niche, but still, it should be waterproof. Sloppy work, hopefully, not indicative with the rest of the shower's construction. RedGard is a decent product, but only when it is applied per the manufacturer's instructions. Mortar and tape over seams is a good thing, but then you need the required thickness of the membrane applied. That gap shouldn't be too big.

There are some preformed, foam, tileable niches that are waterproof when installed properly, but they don't give you the flexibility on size like a custom one.

Thank you, Jim. Sorry to bother you further, just had a couple quick questions on mortaring with the cement or taping over seams - is that usually the way to help with waterproofing? (Before you Redgard of course.)

And when you talk about the "required thickness" of the membrane, do you mean the Redgard applied needs to be just as thick as the mortar, or that it should be at least two coats?

The gaps between different pieces of cement board (of whatever kind) are supposed to be filled in completely with thinset mortar, and covered with fiberglass
mesh tape, per c.b. manufacturer's instructions and standard tile industry practices. Any use of Redguard as a waterproofing membrane is supposed to be CONTINUOUS
and of adequate thickness (typically requires multiple coats), and wherever there is a change-of-plane joint, there is supposed to be a reinforcing layer of fiberglass
mesh tape embedded in the Redguard. This is all according to Mfg.'s instructions. Your contractor's work is abysmal, and you are well within your rights to insist that
they rip out their junk and build it correctly. Your shower stall needs to be waterproofed, and neither mortar nor tile nor cement board are waterproofing materials.

Thank you - much appreciated....