I’m remodeling and installing a steam generator for the shower, which will be ceramic tile on cement backer board.
I’ve read a lot of horror stories about moisture infiltration into the stud cavities, and I’d like The Word on proper moisture/vapor barriers. I’ve read that a single sheet of crosslinked polyethelyne is the way to go…some say that 6 mil from the Big Box stores is NOT the way to go, and that a more specialized product is needed.
I wonder about nail penetrations in polyethelyne — should they be sealed, and if so with what material? I’ve thought of using a product such as Bituthene (Grace). All I can get for certain is that asphalt-impregnated building paper is not the way to go.
I would appreciate input on this — case histories, successes, whatever.
Thanks very much.
Mike
Replies
A product I used and liked is called WEDI. It is a rigid foam board with a cement coating on each side. It's waterproof on the surface, instead of behind near the studs.
Real easy to work with: Screw it to that walls like regular cement board, seal the seams with mesh and caulk, seal the screws with caulk, tile over it. Very light, and you cut it with a utility knife.
Hi Mike,
Cement board alone isn't going to give you the vapor-impermeability that a steam shower requires. And bituthane does not like the alkali from cementitious mortar. The TCNA has two recommended shystems for steam showers; SR613 and SR614. SR613 is a fully-rendered vault of cement mortar, which is likely beyond the skill level of a non-specialized contractor. SR614 calls for cement board to have a vapor-proof membrane bonded to it.
Schluter Systems offers their KERDI membrane for the SR614 application, and it's relatively easy to install. The Noble Company has Wall Seal. Both have a permeability rating of "less that 1", which is required for steam shower construction. None of the liquid-applied membranes have a permeability rating below 1 however and none are suitable for use in a steam shower.
Another alternative, although not yet listed by the TCNA in their handbook, are the foam-core backer boards from either WEDI or Schluter Systems. Both are based on a core of extruded polystyrene foam and have a slight thermal insullation advantage over cement board. WEDI products have a cementitious-latex coating applied to both sides and thinset is use to bond directly to this. Schluter Systems is launching their new KERDI-board product line at the end of April and it will feature their KERDI membrane pre-bonded to the foam core. Both require that all of the seams and penetrations be sealed with urethane sealants and the Schluter System also allows for their patented KERDI-band and KERDI-Kereck pre-formed corners to be used. Both systems offer pre-formed shower pans for a completely modular system.
I'm looking forward to the KERDI-board release but I currently tend toward the WEDI system.
Shaughnn
Two recommendations, for what it is worth.
Schluter Systems Kerdi membrane. I am in a very small market, but from what I know of it, all the steam showers done here since steam became the rage, have been Kerdi lined. We've just a half-dozen tile contractors.
And you don't even need cement board.
John Bridge Forum. Your online source of information for all things tile, used by many more professional tilesetters than view this forum. Huge numbers of threads there about steam shower tile installations.