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airforce mom 10-02-2011 08:07 PM

moisture proofing with plastic sheeting
I am having someone help me remodel my bathroom. We tore out the old tile in the shower and my friend just put up some green board, and now is going to tile over that. Should he have used cement board instead and should he have put some of that moisture proof plastic sheeting between the insulation and the green board. . Help!! :(

OhioHomeDoctor 10-02-2011 08:10 PM

Vapor barrier is necessary on outside insulated walls. If you are going to leave the green board make sure you waterproof it with fabric or roll on membrane. We most of the time, rock board then fabric. Even on tub walls.

airforce mom 10-02-2011 08:44 PM

I'm not sure what you mean by rock board and what type of fabric or roll on membrane?

Gary in WA 10-02-2011 09:09 PM

Check with your local Building Department.

R702.3.8 Water-resistant gypsum backing board. Gypsum board used as the base or backer for adhesive application of ceramic tile or other required nonabsorbent finish material shall conform to ASTM C 1396, C 1178 or C1278. Use of water-resistant gypsum backing board shall be permitted on ceilings where framing spacing does not exceed 12 inches (305 mm) on center for 1/2-inch-thick (12.7 mm) or 16 inches (406 mm) for 5/8-inch-thick (16 mm) gypsum board. Water-resistant gypsum board shall not be installed over a Class I or II vapor retarder in a shower or tub compartment. Cut or exposed edges, including those at wall intersections, shall be sealed as recommended by the manufacturer. From;

Here’s the bad news; R702.3.8.1 Limitations. Water resistant gypsum backing board shall not be used where there will be direct exposure to water, or in areas subject to continuous high humidity. From;


Blondesense 10-03-2011 11:39 AM

You do not want any drywall or gypsum product in a shower or wet area. Moisture resistant or not. If water gets to it, and it will eventually, it will turn to mush and grow mold.

Bud's blog is a good place to start.

Bud Cline 10-03-2011 12:07 PM

Moisture resistant wallboard for wet areas was outlawed several years ago as above stated. The only time it is acceptable is if a total water resistant barrier such as Schluter's KERDI Mat is used. It is required on the ceiling also.

When applying a waterproof barrier to the surface of the substrate you do not use a moisture barrier at the studs.

Cement board is the proper product to use, never drywall, moisture resistant or not.

Rock board = cement board.:)

airforce mom 10-03-2011 02:59 PM

thanks for all the info, it seems as though we may have to tear out the greenboard and use cement board, better now then a few years down the road and we have a mess

Bud Cline 10-03-2011 03:09 PM


thanks for all the info, it seems as though we may have to tear out the greenboard and use cement board, better now then a few years down the road and we have a mess
Now's the time to do it right.:)

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