My dad told me to use a 3/4 inch plywood base for my tile floor, and he was totally right

I was redoing my bathroom floor and almost went with the cheaper 1/2 inch stuff to save a few bucks (about $40 total). He insisted the thicker plywood would prevent any flex and keep the grout from cracking. I listened, and after a year, the floor is still perfectly solid, no cracks at all. My neighbor used the thinner stuff on a similar project and already has hairline cracks appearing. Has anyone else had a similar experience with subfloor thickness making a big difference down the line?

2 comments

2 Comments

the_kelly23d ago

My uncle's kitchen reno used 5/8 inch over the joists and we still ended up with a few cracked tiles after two winters. We had to tear a section out and put down 3/4 inch exterior grade plywood as a new underlayment. The extra stiffness from that thicker base made all the difference, zero movement now.

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benlewis23d ago

That's a solid data point. Did your uncle check the joist spacing before the first attempt? Sometimes 5/8" is fine over 16 inch centers, but if those joists are 24 inches apart, it's just not enough meat. Also, was the plywood glued AND screwed down, or just nailed? That bonding method can be a game changer for stopping flex.