Proper subfloor thickness for porcelain tile?

cruzmislMarch 16, 2013

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.

Thanks!
J.

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longtimer

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.

    Bookmark   March 18, 2013 at 11:56PM
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aliceinwonderland_id

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

    Bookmark   March 19, 2013 at 5:19PM
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brickeyee

How big are the tiles?

Larger tiles require stiffer substrates.

    Bookmark   March 20, 2013 at 12:57PM
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StoneTech

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

    Bookmark   March 21, 2013 at 12:49AM
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