Greenboard No Longer an Approved Substrate for Tub and Shower Areas The International Residential Code (IRC) has determined that effective January, 2006, paper-faced greenboard will no longer meet its standards as an approved tile backer substrate for wall tile in wet areas such as tub and shower areas. IRC, Chapter 7 - Wall Covering Quote: 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 630 or C 1178. 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 (13 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 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. 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. The new requirements are: R702.4.2 Cement, fiber-cement and glass mat gypsum backers. Cement, fiber-cement or glass mat gypsum backers in compliance with ASTM C 1288, C 1325 or C 1178 and installed in accordance with manufacturers� recommendations shall be used as backers for wall tile in tub and shower areas and wall panels in shower areas.

I want to know if our contractor used the proper materials behind our "direct-to-stud 3-piece tub surround (it has a seamless look, but it's 3 panels for the 3 walls plus a bathtub). Behind the tub surround, the contractor installed regular QuietRock soundproofing (he didn't use QuietRock ES Mold Resistant). Then he installed XP Gypsum (purple) Board. Then the tub surround walls. He installed purple board for the walls above the tub surround over the flange of the tub surround. Is this setup fine / up to code, or should he not have installed purple board behind the tub surround panels? The Gypsum Board manufacturer's web site states that "XP Gypsum Board should not be used as a backer board directly behind tile and wall panels in tub and shower areas." I also read on a web site: "When installing a monolithic tub and shower enclosure (e.g., fiberglass with no seams), know that cement board or an equivalent is not required, but all paper-faced backerboard must meet ASTM mold-resistant standards." Well, I don't have a monolithic tub enclosure, so according to this site, you're not supposed to use paper-faced backerboard behind a non-seamless tub/shower enclosure. However, my enclosure is a direct-to-stud type of installation, so I don't know if this also applies to my enclosure. Since the contractor had to soundproof the walls, he installed purple board over the QuietRock. I'm totally confused as to whether or not he should have installed the purple board behind the tub enclosure or whether he should have installed cement board along with a waterproof coating. Thank you so much for any info and help.

In addition, make sure that your shower valve trim kit will still fit with the added wall thickness. There's usually a bit of leeway. Just make sure you'll be on the correct side of that leeway. Depends on the layout of your room, but think ahead and figure if adding another layer on the wall will result in the edge of the cement board showing versus the edge normally being butted to and the face flush with the non-shower walls in the room. I hope that makes sense. Not exactly the situation I'm referring to, but close: cement board edge And it's probably obvious, but if you add cement board over the gypsum, you'll need screws or nails long enough to go through the greenboard and get proper purchase in the wall studs. Do not use drywall screws. And lastly, the first sentence of your post..."I started remolding my bathroom." Had you tiled directly on the greenboard, you may have very well been doing just that. lol Probably the easiest thing in the end? Remove the greenboard.

It probably goes without saying that showers are supposed to be installed before drywall. And certainly before paint. Perhaps they were on backorder? When I replaced shower surrounds like this, I had to trim over the edges because of the design. Anytime you use mud near a shower, you can have issues. That would seem to make sense but it was really driven home when I had to cut an access hole in the ceiling of a 10 ft high bathroom. I patched it in the usual way and it kept eventually cracking. So I had a pro redo it. And it eventually cracked. So now I have trim covering the original cut out so that it looks like an access panel but the trim is just covering the cracks. Now I am sure that you can do it appropriately but it will never be as stable as wood - or even better - PVC. Another thing. I had a bargain basement build in zone 3A and they still mandated air barrier behind the shower 12 years ago. Zone 3A is pretty warm and generally things get less strict as you move south but you probably should always have it. There does not appear to be any in your build. No endorsement of this link but it has a pic demonstrating how you should see the air barrier if you can see the top of the shower. https://thehtrc.com/2014/air-barrier-behind-tub-shower