I'm in the middle of remodeling my bathroom in a house built in the 1900s. The floor has 5/8th inch planks running perpendicular to the joists, and it seems pretty level without any creaking. Here's what I plan to use for the flooring: 3/4 OSB secured with 1 5/8th deck screws, then thinset, followed by 1/2 inch cement board with EdgeGuard and 1 5/8th cement board screws, and finally LVP. I'm wondering if this setup is sufficient or if I need additional waterproofing? I've heard that cement board plus fibertape and thinset, along with the LVP, should provide enough waterproofing, but I'm open to suggestions. If cement board isn't necessary, would replacing it with 1/4 inch plywood be enough?
2 Answers
You won't need cement board if you’re not planning to install tile. However, if tile might be in your future plans, now’s the ideal time to put it down under everything for a solid base. Just keep in mind that if you roll with LVP, the surface beneath has to be super smooth since LVP can reveal any imperfections underneath. It's crucial to follow the manufacturer's guidelines here. Also, cement board isn’t inherently waterproof; for that, you’d need a separate waterproofing layer. A product like RedGard could provide extra protection in case of any spills or mishaps, especially with kids around—better safe than sorry!
Yeah, I get where you're coming from! It's always good to have that extra layer of defense just in case. Better to be safe with kids around!
Why are you even thinking about using cement board? Just go for OSB and put down a 1/4 inch plywood underlayment that's designed for LVP—skip the thinset entirely!
I appreciate the advice! I read somewhere that cement board is best for waterproofing in bathrooms, but maybe that applies mainly if you’re tiling everything.
Thanks for the insight! I want a solid floor, and it feels like cement board is sturdier than plywood. We're a no-tile household for sure, but I appreciate the heads-up on the waterproofing. The LVP we chose is thick and claims to be waterproof on its own, but it seems almost too good to be true. I’m definitely considering that membrane idea you mentioned!