Designing Kitchens and Bathrooms - Leaky built-in shower

Ten years ago we had a respectable bathroom design company install a custom built-in shower. Three walls are tile. One wall is custom glass with a glass door, both sitting on a tiled 6" lip. There is also a built in tiled bench (plywood covered with ABS). Several years ago the shower developed odd leaks evidenced by discolored dry wall along two walls outside the shower and powdering, discolored grout all along the lip. I regrouted and resealed the inside edges with silicone. That worked for a while. The problem is now back and is worse. I cut out the dry wall and found the framing very wet near the bottom and a sticky layer of mud on the floor. The drywall on one wall was wet 18" up and nails were badly rusted. My problem is that with the exception of an 16" span along the lip (where grout along the lip is powdery and many tiles along the inside and outside are lose) I cannot figure out what is leaking. The glass wall *seems* properly seated and sealed. The tiles on the built-in bench seem firm, and the grout looks... well, not great but serviceable... and not like it could be the source of that much leakage. Not sure where to begin with this one.

It sounds like the shower pan liner is leaking. This liner is installed over the morter bed, then morter poured over the top. This liner should extend up and over your 6" lip and about 4 inches of the sides of the walls.

I suspect this to be leaking, and if it is, probably means a complete tear out of part of the walls and all of the floor.

Also observe where the floor tiles and the wall tiles meet. There should be caulk in these areas and not grout. Since these two opposing parts (walls,floor) might have a small shift, it will cause the grout to crack and then leak.

Obviously the best route would be to inspect ALL the grout lines for cracks.

The shower drain may be another cause for the leak.

Unfortunatly, this fix may require the destruction of your shower.

Hot: I suspect you are right. The mud on the floor behind the wallboard would seem to be the clincher. OTOH, because tearing out and starting over is such a pricy/messy option, I expect I will give regrouting, caulking, and sealing one more try. Any suggestions on what I might pillage before burning this one?

Cheers
Beekeeper

Your shower has reached the end of its useful life. 10 years is not that old, but when its constructed the way you describe, your lucky you got that long out of it. There should be no drywall used in a shower. The walls should be cement board, and they should have a vapor barrier behind them to keep moisture from reaching the framing. When you say abs over the bench, are you talking about a pan liner material like the one that was used in the shower pan. If so, thats more problems. Anytime you have a framed bench seat in the shower, it has to be covered with cement board and a paint on membrane like redgard should be used over the cement board. The waterproofing needs to be done on top of the plywood and cement board so all screw holes are waterproofed. If pan liner material was used and plywood installed over it, you now have lots of holes in the pan liner. Tile and grout are not waterproof, and when water gets under them it finds the holes in the pan liner material. Once wood and drywall get wet, you have lots of swelling (which kills the tile and grout) and mold issues. There are other ways to make a custom shower like the kerdi system, but since your contractor didnt do the basics right im assuming he never heard of kerdi.

Once drywall is exposed to water it wicks it up like a sponge. Ive seen drywall wick water all the way up to an 8' ceiling from water leaking on to a floor for a prolonged period of time. Its hard to pinpoint leaks just from looking at the back of wet drywall.

I didn't even think about the drywall. Needless to say, the shower should be ripped up.

This is a DIY forum Bee, so you can come here for instruction on how to rebuild this shower if you so choose to tackle it.