durock directly to 2x8 t&g subfloor?

Hi All,
Bathroom project coming up. Part of it is to replace a wood parquet floor with ceramic tile. Parquet is 3/8" thick over 1/2 or 5/8" particle board over 2x8 T&G subflooring (nominally 1-5/8" thick). I'm concerned about achieving the same level on the new floor.
Can I remove the particle underlayment and screw concrete backer board (Durock aka Hardi-backer, etc.) directly to the T&G subfloor? My instinct says it is stiff enough without additional plywood underlayment. If I have to put a plywood base on top of the T&G I have no hope of getting the tile floor to the same level as the current floor.
TIA,
Casey
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YES YOU CAN
C.A.

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KS7J wrote:

Read this: http://www.ttmac.com/deflection_limitations.htm
And forget the screws on the underlayment. You can apply the underlayment over the T&G using tile mastic and 1-1/4" roofing nails.
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That raises a further question: I need a vapor barrier somewhere above the T&G subfloor, I would have put it directly on top of the T&G then put the Durock on top of that. Obviously, mastic is going to do no good on top of the vapor barrier. Does the Durock, taped, provide a vapor barrier?
TIA,
Casey
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OK, one last followup (I hope).
Can I use thinset as a leveler over the 2-by subfloor? There is some uneven-ness between the boards, maybe 1/8" at most and I'd like to use the 1/4" wonderboard if possible (the subfloor is very solid, btw).
If I sand down the subfloor a bit, will the adhesion be sufficient for the thinset? Then I plane to use tile mastic on top of the thinset skim coat, wonderboard (durock) nailed on top of that and taped with fiberglass tape and thinset. Lastly, the floor tiles.
Sound OK?
- Casey
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