Heard a contractor say never use self-leveling compound on plywood subfloors

I was at Home Depot last weekend and overheard a flooring guy tell a customer that self-leveling compound will crack if poured directly on plywood. He said you need a primer or a crack isolation membrane first, otherwise you're just wasting $50 a bag. I've been planning to level my basement floor before laying LVP, and I always thought you just mix and pour. Now I'm second guessing my whole approach. Has anyone here tried using a primer like this? Did it hold up through winter?

2 comments

2 Comments

colesanchez22h ago

Check if that contractor meant the compound needs a latex-based primer or a specific epoxy primer for plywood, because those two handle moisture and flex very differently. I used a cheap acrylic primer once and got hairline cracks by spring, but a buddy swears by the expensive roll-on stuff from Mapei and hasn't had issues. What exactly did he say was in the primer he recommended?

ward.mason20h ago

People get way too hung up on primer types for a plywood subfloor. Unless you're building a shower pan or flooding the room regularly, any decent bonding primer will hold up fine. Save the overthinking for something that actually matters.