In placing new tile in a foyer, is it ok to lay the plywood subfloor on 2 x 2's at 16" apart due to 4" depth

Question

The area is about 4-6" deeper than the adjoining kitchen floor. By adding the 2 x 2's I can raise the level and make both rooms equal in level. By doing this, would the area between the 2 x 2's make the subfloor too weak for the tile and grout and result in cracking?

Answer 1

Yes, but use 3/4 in plywood AND concrete backerboard. Even thick plywood will bend.

Nail plywood down every 6 inches the whole length of al the 2x4s.

Nail or screw the backerboard down every 6 inches squared.

If you need to shim the floor up a little to meet the kitchen level, be sure to glue the shims UNDER the 2x4s.

Answer 2

Cement is a good idea, but if you stick to the span rating of ur new subfloor you can space accoridingly. 3/4 plywood has a span rating of about 22 inches. I'm not sure for 1/2 but it's always stamped on the bundles in what looks like a fraction, but is the span rating. If u used 3/4 in plywood and spaced ur 2x2s 18 in. apart u should not have to fill the space. Be advised, any motion of the subfloor will cause tiles to come up if u use a thinset, or cement adhesive. I always use mastic, even carpet adhesive in areas i suspect will produse motion.

Answer 3

Yes, it will move and result in cracks. use the 2x2's then fill in with cement. This will be similar to the old bathroom tile floors put down in the 20's that still haven't cracked. As long as the area isn't huge the added weight wont be an issue. (I'm assuming your existing floor is sound and stable.)