Adding 1/4 Ply to 5/8 subfloor

Subfloor is 5/8 plywood. It's mostly good save for a couple spots that were soft, one shown here under repair. I have the wood sash around the stairs I want to match height with at 1.375" from subfloor. Tile is 3/8" thick. I figure 1/8" mortar, 1/2" durarock, 1/8" thinset, puts me at total height of tile floor of 1.125", 1/4" shy of my target. Could I add a 1/4" plywood layer on top of the 5/8" subfloor safely? The little extra thickness would help level everything out as well. A lot of mixed reviews as I search around saying yes, some saying the thickness of 1/4" even when added to the 5/8" represents a risk of flexing too much indepentently. If not a great plan, what other options? Hoping to not have to rip out 250sqft if subfloor to go to 7/8" ply. submitted by /u/fattyfatkid02 [link] [comments]

Apr 26, 2025 - 04:36

Subfloor is 5/8 plywood. It's mostly good save for a couple spots that were soft, one shown here under repair. I have the wood sash around the stairs I want to match height with at 1.375" from subfloor. Tile is 3/8" thick. I figure 1/8" mortar, 1/2" durarock, 1/8" thinset, puts me at total height of tile floor of 1.125", 1/4" shy of my target. Could I add a 1/4" plywood layer on top of the 5/8" subfloor safely? The little extra thickness would help level everything out as well. A lot of mixed reviews as I search around saying yes, some saying the thickness of 1/4" even when added to the 5/8" represents a risk of flexing too much indepentently. If not a great plan, what other options? Hoping to not have to rip out 250sqft if subfloor to go to 7/8" ply.

submitted by /u/fattyfatkid02
[link] [comments]