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Discussion Starter · #1 ·
Hi,
I'm preparing a kitchen remodel and want to make sure that I have a strong enough subfloor for ceramic tile. The house is from 1958 and has diagonal planks over floor joists. The kitchen has now a 3/4" plywood and two layers of vinyl flooring. The rest of the house has 3/4" hardwood floors. I know I'll end up higher than existing hardwood, but don't want it to be "too much". Initially I thought I'd use 1/2" plywood, radiant heat cable embedded in self level concrete and thinset with tile. But is a 1/2" plywood enough? Or should I use 1/2" durock or similar cement board over the planks?
Do you have any other suggestions?
I also talked to a tile guy and he suggested using a thin mesh type material (1/8") embedded in thinset between plywood and self level concrete. Supposedly it doesn't transfer movement and thus prevent cracks. But that would bring it up another 1/4" or 3/8". Is there any way I could keep the height difference under an inch?
I appreciate your ideas and opinions.
Thank you.
 

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The first thing you need to do is get those 2 layers of nice, flexible, tile cracking vinyl off there.

Then, I would say another 1/2" plywood and then 1/2" CBU would be ok.

Is this for your house or a customer?
 

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No--do not add cement board over planks--they move to much and will cause floor failure---Add BC exposure 1 plywood over the 2x6---

If you are embedding coils in self leveling compound,there is no need for cement board---the SLC is fine for setting the tile---

Come back with your joist size--spacing and unsupported length and someone will check the deflection for you--Mike----
 

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It sounds to me like you have 3/4" diagonal sheathing, then 3/4" plywood. This should give you a good sturdy floor if your joists are sized properly and haven't been butchered on the underside too much.

You probably have a 24' wide house with 2x8 floor joists, or a 32' wide or less with 2x10's. Do report back with a report on your floor joists.

Is the wood on the same type of sheathing? If that is the case, then your 3/4" wood is on top of the diagonal sheathing and 3/4" plywood, so it is up above the vinyl? If so, you'll have a good chance of getting your floor surfaces to flush up.
 

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Discussion Starter · #7 ·
I apologize... I didn't know about your strict rules here. This is actually for my own home, and yes, I am a contractor (mostly exterior remodeling, though - not a flooring expert).
The floor joists are 2x8 with a 12ft span spaced 16" apart.
And the hardwood floors are on top of the diagonal boards, so the vinyl is 1/4" to 3/8" higher right now... that's why I was wondering if I could reduce thickness of the subfloor.
If I offended any BIG contractors here, I apologize again... you don't have to answer :no:
 

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If you have access, you can always beef up a subfloor from below. Google the term Ditra, and look up the specs it requires and go from there.
 

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If your joists are 2x8--16" centers--12 foot unsupported---then your deflection is 302.

360 is required for safe ceramic install--720 for natural stone.

I think you may need to beef up the joists in order to install that heated floor with confidence.

Thank you for being straight forward with your tiling experience---as a tradesman,you understand using the best practice is always cheapest in the end.
 
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