Had to choose between a 3/4 inch plywood subfloor or 1/2 inch with an extra layer for a big tile job

The old floor was uneven and the homeowner wanted 24 inch porcelain tiles. I could either tear out the old subfloor and put down new 3/4 inch plywood, or add a layer of 1/2 inch on top of the existing. I went with the 3/4 inch new plywood because it gave me a perfectly flat start. It cost about $400 more in materials and added a full day of work. The install went smooth and the floor feels solid as a rock. Anyone ever gone the other way and added the extra layer on top? How did it hold up?

3 comments

3 Comments

blair_dixon13d ago

Did that friend happen to mention if the old subfloor had any give before he added the extra layer? My buddy Mark tried something similar in his bathroom, put half inch over a slightly bouncy original floor, and within a year a couple of the grout lines near the shower started cracking. He pulled up a tile and said the plywood underneath had started to cup a little along the edges, probably from moisture and just not being flat enough to begin with. He ended up ripping it all out anyway, so the extra labor and materials just got doubled.

kevin_murray883mo ago

Man, a buddy of mine tried the add-on layer route last year. He put half inch over his old kitchen floor to save time. He said it felt okay at first, but after a few months some of those big tiles started to get a little hollow sounding in spots. He's pretty sure there was just too much flex hiding under there. He told me he wishes he'd just ripped it out like you did.

josephs263mo ago

Yeah, that sounds about right. My own shortcuts usually come back to haunt me too, just ask my last DIY project.