View Full Version : Vapor barrier needed?

04-16-2007, 12:00 PM
I have my basement bathroom fully studded, wired, and plumbed. I have the fart fan installed and vented. I am ready to install the plastic shower floor, durock, and then ceramic tile the shower.

This bathroom has no walls near the exterior walls. Do I need to use a poly film vapor barrier between the studs and the durock in the shower? Do I need to use the poly film vapor barrier between the studs and WR drywall in the rest of the bathroom? What are the pros and cons of using / not using a vapor barrier for this application?


04-16-2007, 03:08 PM
Well, unless required by your local codes, the WR wallboard is no longer part of the national codes...

Most locales require a shower to be built to the guidelines in the Tile Council of America (TCA) handbook. Short answer...yes, put a vapor barrier behind the cbu on the walls of the shower and run it down over the top of the flange on the pan. If the other walls are not an exterior wall, no problem. Make sure to follow the manufacturer's directions on the number of screws and to install the alkalie resistant reinforcing tape to the seams. You can do that while tiling to prevent 'speed bumps'. It isn't like mudding a drywall seam - it isn't to look pretty, but to reinforce the seam.

Unless prohibited by the manufacturer (unusual), you will get a lot more life and enjoy it better if you bed that pan in mortar to fully support it since most of those things a flimsy when walking around on them.

A really good place to ask tiling questions is www.johnbridge.com (http://www.johnbridge.com).

04-16-2007, 03:16 PM
what Jim said.

Grout is porous. A shower made of Durock CBU needs plastic behind it going down into the pan, past the edge of the Durock, to make water drip into the pan.


04-16-2007, 04:07 PM
Definitely planning on putting something under the plastic shower floor / pan (Mustee 32x48).
What would work best? A buddy gave me half a bag of thin set. He said he did his with that. An expert (?) at my local Homer said to use the sand mix Quikrete.

Also, another buddy of mine, a tile and stone guy, gave me some grout sealer in an orange jug with all german wording on it. He says it is the best stuff ever for sealing grout - it's all he uses. It's really stinky stuff. Any comments / experience?


04-16-2007, 07:32 PM

About any concrete product: they are all incompressible. Any one will do the necessary thing that you want it to do. Be incompressible.

It is good news when someone gives you a few dollars' worth of concrete, any concrete.

First thing about the sealer: It won't ever be a replacement for a vapor barrier.

Great that you got some sealer.


04-16-2007, 07:51 PM
Most thinsets don't work well over say 1/4" thick unless labeled medium bed. Depends on how much gap there is under the pan to the floor. The sand mix is probably the cheapest thing if you had to buy it - it's mostly sand, but is what they make shower pans from most of the time. It probably is a 3-1 sand/cement mix, which is a little richer than a shower pan, but that's probably good since you won't be putting tile over it.

Orange, lousy smelling sealer? Hard to tell without really knowing what it is. Unless it is an enhancing sealer, most I've seen are basically clear. Not sure what you have there.