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.
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.