PSA: My lesson on checking subfloor flatness before glue-down

I skipped the flatness check on a recent glue-down job to save time. Now I'm dealing with bumps and hollow spots that are a pain to fix. What's your go-to method for making sure the subfloor is ready?

3 comments

3 Comments

gavin_jones101mo ago

Skipping that check is always a trap. My go-to is a long metal straightedge, something like a six-footer. You slide it across the floor and look for any gaps under it bigger than a dime’s thickness over ten feet. Those hollows will telegraph through and the adhesive won’t bond right, leaving you with soft spots and eventual failure. Fixing it after the fact means pulling up boards and grinding down high spots, which takes ten times longer than just checking first.

eric_martinez1mo ago

My eight-foot level does the same trick. Learned that lesson the hard way when a whole section had to be ripped up last year.

fiona_walker1427d ago

That sinking feeling when you see those bumps come through is the worst. Been there myself, and it's such a frustrating fix. Gavin's straightedge method is spot on for finding those gaps. A long level works too, but you really need that full length to catch the dips over distance. It feels like a tedious step when you're eager to lay floor, but it saves so much grief later. Nothing bonds right over an uneven base, and you end up hearing every hollow spot with your feet.