Flooring Tile - Ceramic Tile over MDF Board???

I have a concrete floor porch that 10 years ago was enclosed to make another interior room. (It has never had any moisture problem).

We have decided we wanted the floor of this porch to be the same height as the existing floors, so I took 2x4 PT wood on 12" centers and installed on top of the concrete floor (it is level). I mistakenly did not get any advise and thought 3/4" MDF sheets would make a good underlayment and would install 18x18 ceramic tiles over it. (The finished tiles would then be the same height as other tile floor in adjoining room).

I have since learned that the 3/4" MDF board was a bad choice. Can this be used or do I need to rip it out... couldn't some type of leveling thin set be put over it???

If I have to rip it out, what can be laid on top of the 2x4 "runners" to make it 3/4" thick???

Desperate in Tampa Bay...

The only plywood suitable for tile is exterior grade plywood,c.d.x. ply.
It needs to be 1 1/4 thick to be able to support the tile,anything less you are rolling the dice my friend and it is destined to fail,you could just reduce it down and install durock over that then there would be just a small transition there at the door other than that you would be tearing it out and redoing the sleepers under the M.D.F. board and lower them down to the right heighth :cool:

Floorman, go back and reread the original post!

This is over concrete, that they are trying to raise the height. Not over joists. 1¼ would be overkill.

I say rip it out and find a poured self leveling product.

www.Ardex.com

I think you need to reread the post perry he already has the sleepers in and the plywood down and is wondering what to do WITHOUT tearing out what he has already done.Yes you can TEAR all that out and start over as i stated in my post,but that is not what the question was Perry :cool:

This floor probably has no deflection, the best situation. The prob is the MDF. If it were me I would apply some sort of isolation,anti fracture membrane, and tile right over it. Tape the joints before or after applying the membrane. Whatever is reccomended. You should back butter all the tiles especially the corners. I would, as always, consult with the adhesive manufacturer before doing anything. They may have 1 product that will solve all your probs. I hope this room is not a 8 by10 with less than 3 sheets 'cause then the answer is a no brainer unless it is glued down, rip it out

I think you need to reread the post perry he already has the sleepers in and the plywood down and is wondering what to do WITHOUT tearing out what he has already done.Yes you can TEAR all that out and start over as i stated in my post,but that is not what the question was Perry :cool:





This dang crow, is one tuff bird to swallow :)


OOOPs!
carry on!


Now that I have reread it again(I totally missed the 2x4 sleepers) :)

Since they are on 12" centers and not a full 16" as a floor joists are, you my be able to get by with the ¾" CDX plywood.