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I am considering using Hardybacker for a floor and wall, and noticed that the instructions do not require felt between the Hardibacker and subfloor, nor plastic between the studs and the hardibacker.
I assume I should still put 15-30 lbs of felt on top of the subfloor and a vapor barrier between the studs and the board.
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It's my understanding that the standard procedure for installing Hardibacker or other cement board to a subfloor is to apply thinset to the subfloor, drop the cement board over it, and nail the cement board down. This doesn't seem to accommodate a felt layer. Plus, it'd serve no purpose that I can see -- not the same as under hardwood flooring. Since neither grout nor Hardibacker is impermeable, I'd believe the application of a waterproof membrane behind the Hardibacker on the bath wall would make sense.
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Tommy,
Barry has it right: thinset (no felt) under the between cement board and subfloor and Roofing felt between the studs and the cement board walls. But your question indicates that you may have many more questions about what you are doing,(is your sub-floor sufficient, for instance?) check out the ceramic tile articles in old FHB's or these web sites:
http://www.tdionline.com/
http://www.tileusa.com/
http://www.usg.com/
http://www.jameshardie.com/usahome.htm
There are also several strings on cement board in the archive.
CLG
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I am considering using Hardybacker for a floor and wall, and noticed that the instructions do not require felt between the Hardibacker and subfloor, nor plastic between the studs and the hardibacker.
I assume I should still put 15-30 lbs of felt on top of the subfloor and a vapor barrier between the studs and the board.