Why does nobody talk about the 3/8 inch gap rule for vinyl plank in basements?

I used to think you could get away with a 1/4 inch gap around the edges in a basement install, especially with a floating floor. Then I did a job in a 1970s split-level last spring, and the homeowner called me back 8 months later because the planks had buckled near the exterior wall. The basement had shifted just enough with the seasons. Now I always leave a full 3/8 inch and use a proper undercut saw on the door frames. Has anyone else had a floor fail from not leaving enough room to move?

3 comments

3 Comments

mark6762mo ago

Learned that the hard way too. My first basement job looked great for about six months, then it looked like a tiny mountain range.

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andrew_kelly2mo ago

Moisture probably came up from the floor, right?

roberts.jordan1mo ago

Moisture coming up through the slab is a huge issue a lot of people miss. I read a good article that explained how concrete acts like a sponge, pulling water up from the ground. Even if the floor looks dry, that hidden moisture can ruin flooring and paint over time. A proper vapor barrier under the slab is key, but many older homes just don't have one. Testing for moisture before finishing a basement is the only way to know for sure what you're dealing with.