1/2 Hardibacker Floor?

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wrote:

Liam,
The original post said he had a 1/2" ply sub, which I think everyone can agree is totally sub-standard. Then the OP talked about ADDING 1/4" ply and then 1/2" Hardibacker; still likely not up to snuff.
My response was to ADD 1/2" ply, for a TOTAL ply thickness of 1", then use 1/4" Hardi. That said, he should still look at the quality of the 1/2" ply currently in place. Considering the original builder used such a inadequate subfloor, it may not even be AB or AC exterior.
Your are correct that a professional consult may be appropriate. But, if he can get the substrate up to L/360 specs there is a chance the final install will work.
DLG
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snipped-for-privacy@svs.com (G. Mark Stewart) wrote in message

From the Hardibacker site: ------------------------------------------------------------------ For all floors:
Use minimum 5/8" exterior grade plywood or 23/32" exterior grade OSB, complying with Local Building Codes and ANSI A108.11, over joists. Joists' spacing not to exceed a maximum of 16" on center.
Deflection must not exceed L/360 of the span, including live and dead design loads.
Do not use glue between grooves of tongue-and-groove subfloor to allow for expansion and contraction of subfloor." -----------------------------------------------------------------
Now that said, The key is the L/360 deflection rule. Also, the OSB grade is important, especially with the marginal floor thickness. The thicker 1/2" backer over 1/4" plywood won't help that.
My advice? saw out the subfloor as close to the cabnets as you can and replace the 3/4" OSB (screw & glue). Shim the remaining floor with 1/2" plywood fillers (screw & glue). Use thinset under the 1/4" backer and attach with recommended screws or nails (lots of debate on attaching...).
You are then ready for tiling. Anything less...is a gamble.
-- Bill (who recently replaced a bathroom floor with 1-1/8" OSB...just to make sure)
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snipped-for-privacy@mail.com (Bill) wrote in message

Well, thanks for all the input folks. I've got a pretty good idea on how to proceed.
Mark
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