I am removing a laminate tile floor. There looks to be 2 layers of 3/4" Plywood as the sub-floor. Do I remove 1 layer of Plywood and install 1/2" concrete board or leave the plywood and install 1/4" concrete board on top of the plywood before installing the porcelain tile floor? My concern is that if I leave the existing sub-floor material I am going to have a ½” rise in the floor from one room to another.

  • This isn't easy to answer. You can probably get rid of one layer and go with cement board but the extra plywood might be needed to provide a solid foundation given joist spacing, load bearing poles in your house and so on. – DMoore Nov 16 '14 at 17:05

wirelath nailed over the plywood(overlapping the lath 2",use paper backed lath to avoid moisture of setting/grout materials)nail or staple(pneumatic,not a hand staple)in a 8"x8" grid.wire acts as a trampoline,the thinset gets into the mesh but won't twist when the plywood deflects.normal thin-set is fine in the application(unless a modified is needed for the tile).


Although cement backer board is an ideal substrate for tile, you could bond directly to the existing plywood if it is clean, flat and strong (little or no flex); this is acceptable for areas that see only incidental moisture. There are polymer fortified thin-set mortars specifically designed for direct application to sound plywood flooring that does not exceed maximum deflection specs. I have had very good results, proper application is key. Check it out: fortified thin-set mortar

1/4" cement backer will conform to irregularities in the floor (high/low spots), so if the existing plywood is not smooth and flat I would probably remove the top plywood layer and use 1/2" backer board to give the smoothest flattest surface.

  • I would never do this. Ever. – DMoore Nov 16 '14 at 17:03
  • @DMoore, what would you never do, install tile yourself? Install it per manufacturers directions directly to plywood? Install it on 1/2" cementitious backer board? Successful tile installation depends on numerous factors and requires proper application techniques. I have personally installed tile directly to clean sound plywood with great success, 15 years later it still looks brand new. As stated, maximum substrate deflection must not be exceeded. – Jimmy Fix-it Nov 16 '14 at 17:22
  • Install tile on plywood. You don't know how many homes I have bought with tile on plywood. I can count the number of said tile that wasn't cracked (grout or tile) on zero fingers. – DMoore Nov 17 '14 at 6:59

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.