MR sheetrock

Old 12-21-02, 07:24 PM
David Dickson
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MR sheetrock

What is MR sheetrock and why should it not be used on ceilings?
Old 12-21-02, 10:54 PM
Doug Aleshire's Avatar
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David Dickson,

Water resistant panels are ideal for use in bathroom walls and ceilings (not subject to direct moisture), laundry rooms and other damp or humid areas of the home.Water resistant panels, or greenboard, are specially treated to minimize moisture-related problems.

M/R is not recommended for ceilings where framing is greater than 12" o.c., for single- layer resilient attachment where tile is to be applied. For this reason, you rarely see greenboard on ceilings unless additional ceiling joists are added.

M/R should not be installed over a vapor retarder or on a wall acting as a vapor retarder unless they will not be tiled or finished with an impervious paint. With a vapor barrier on one side of SHEETROCK® W/R Panels, and tile on the opposite, it is not possible for entrapped or absorbed water to escape. Also, the adhesive used in the tile application may not develop a full bond because the vehicle carrying the adhesive cannot evaporate.

You can use 5/8" regular drywall on the ceiling or the M/R with ceiling joist framing of 12" O.C. M/R gets heavy and it doesn't absorb moisture but is resistant to damage. When installed on 16" O.C. it will eventually sag.

Hope this helps!
Old 12-22-02, 06:50 AM
David Dickson
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MR sheetrock

Yes, it sure does. Thanks for the information. I will undoubtedly be back with more questions before I am done with my bathroom replacement. I just finished the kithchen, but the bath and shower present a whole new set of issues. I was extremely glad to find this forum.

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