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Proper subfloor thickness for porcelain tile?

Posted by cruzmisl (My Page) on
Sat, Mar 16, 13 at 18:03

Hi All,
I'm planning on laying down some porcelain tiles in my living room but concerned about the appropriate subfloor thickness.

Currently I have 5/8 plywood glued and screwed to 2x10's which are 16" on center. I have another tile floor that the new install is going to butt up against so I need to plan this properly so I have enough space to level the floor as I go and ensure I don't end up too high

The tile I have measures 11mm thick which is about 7/16". I'm also installing in floor heating which will be secured to the plywood and then completely submerged in self leveling concrete.

Does the self leveling concrete contribute to the floor strength? Meaning, do I still need to add 1/4 or 3/8" cement board (or similar) and then add the concrete or is just the concrete adequate? My gut says the concrete will add the stability required for a porcelain install but I want to be sure.


Follow-Up Postings:

RE: Proper subfloor thickness for porcelain tile?

You need to do one of two things-- either add another 1/2" of plywood and then Ditra (adds another 1/8") or use 1/2" cement board. The 1/2" cement board over what you have is the MINIMUM requirement. You can go over either one with the heating system and SLC.

RE: Proper subfloor thickness for porcelain tile?

longtimer is incorrect. Cement board is NOT structural - it is dimensional. It will not increase your floor strength. You need plywood for strength.

RE: Proper subfloor thickness for porcelain tile?

How big are the tiles?

Larger tiles require stiffer substrates.

RE: Proper subfloor thickness for porcelain tile?

Half inch ply and either Ditra (as above) or quarter inch Durock, thinsetted and screwed.

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