AskCodeMan

Code require cement board for shower enclosures does this include the ceiling where tile isn't being applied. If not what kind of material is allowed? Thanks.

Fully enclosed and separate shower stall, or tub with shower?

I will need to verify this when I get back to my office later, but I do not recall the code requiring cementitous tile backer board, only that the code limits other materials and limits the use of other material to their approved and listed uses.

While standard MR board (green board) is not for use as tub/shower walls, some AHJ allow it to be used at tub/shower walls above the height of the shower arm, other AHJ may not allow green board in that location.

Green board on the ceiling has installation limitation requirements.

From the 2006 IBC: (underlining and bold are mine)
- 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. (Jerry's note: That is not the same as saying that gypsum board shall not be installed in a shower or tub compartment, that sentence includes a specific condition under which the "shall not" applies - i.e., "over a vapor retarder")
- - 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.

- 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. (Jerry's note: That does not state that cement board is required.)

You would need to select the product you intended to use and see if it meets ASTM C 1288, C 1325 or C 1178 and then install it in accordance with the manufacturer's installation instructions.

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.

To me this clearly states that cement, fiber- cement, and glass mat gypsum backers are required for tub and shower areas. That part is clear to me but my question was in regards to what can be used on the ceiling. R702.3.8.1 Limitations Water resistant gypsum backing board shall not be used where there will direct exposure to water, or in areas of continuous high humidity. In you opinion would you allow green board on the ceilings of an open shower/tub? For reference what about an enclosed shower? Thanks for your help

mtCDCcb wrote: ... my question was in regards to what can be used on the ceiling. R702.3.8.1 Limitations Water resistant gypsum backing board shall not be used where there will direct exposure to water, or in areas of continuous high humidity.
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In you opinion would you allow green board on the ceilings of an open shower/tub?
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For reference what about an enclosed shower?

For the ceiling in an open tub with shower (no enclosure going all the way up) - yes.

For the ceiling in an enclosed shower - no.

Jerry,
What would be an alternative finish material in an open tub/shower ceiling. Greenboard is not allowed. THanks.

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.

Here is National Gypsum's product (place cursor over link, right click, select open in new window): http://www.nationalgypsum.com/products/ ... uctID=2372

I tried to get the link to the DensGlass version of the product but the G-P site keeps bringing up page not found errors.

Every major gypsum manufacturer has, I am sure, a similar product, which is basically a gypsum panel with a fiberglass coating of sorts, and the gypsum probably has chemicals added to it to resist uses in wet areas, such as showers, as that is one of the locations they are listed for.