Installing New Shower Base: How to Prevent Leaks

LESLIE: Randy in Delaware is on the line doing a bathroom project. Tell us how you’re working on it.

RANDY: So, a shower stall – an old shower stall – was removed with an old pan just all cruddy and moldy and just outdated. So, installing a new shower base. It’s not a mud base; it’s preformed epoxy and cement. And then, I was wondering about what type of flashing you might recommend from the framing members, behind the corners and any of these areas. How susceptible are they to these moisture issues where the corners may, with expansion and contraction, may break open or get some kind of moisture penetration. What’s the extent of the flashing system that you put behind cement board?

TOM: OK. So, when you put on tile backer board, you don’t flash like you would if you were putting up shingles and intersection – intersecting – with siding. I mean essentially, what you do is you put the pan in, you put the backer board on, you overlap the pan and then you put the adhesive on and the tile right on top of that. That’s sort of the normal procedure for doing a tile job. You don’t really flash the board any further than just making sure it overlaps the prefabricated pan.
Is that what I’m hearing? Are you using a prefabricated, say, a fiberglass tile pan?

RANDY: Right. But a lot of – there are a lot of recommendations out there to run a 6-mil plastic sheet behind the backer board so that any penetration that could occur in the future hits this plastic wall. It overlaps the pan and in front of that, the backer board overlaps it. But anything that penetrates the backer board and the tile and all that hits this plastic and eventually makes its way to the pan, never actually getting to the framing members.

TOM: I don’t have a problem with that. But let me put it to you this way: for many years, the way that tile showers were done is they simply put the green board – the water-resistant drywall – right on top of the studs and that was it; there was nothing more than that. So, by putting on a tile board, you’re already making it a lot more durable. And if you want to put a polyethylene sheet behind that, I have no problem with that. Just make sure that the shower pan that you choose goes up enough to create that good overlap at the bottom so you don’t have water that backs up into it.

RANDY: I think that’s it.

TOM: Alright. Well, good luck with that project. Thanks so much for calling us at 888-MONEY-PIT.