I'm working on my 300 square foot air-conditioned Florida room, which was converted from a porch, and the subfloor consists of three separate concrete slabs. I'm planning to install luxury vinyl plank (LVP) flooring and here's what I've got so far:
1. Grinding down any high spots on the concrete, especially the edges where they meet, to ensure they're level.
2. Using Henry 549 to fill any voids and gaps between the slabs and achieve a level surface.
3. Installing a 6mil poly moisture barrier, then adding Lifeproof underlayment, followed by Lifeproof LVP (which is 9 inches wide, 7mm thick with a 22mil wear layer and is waterproof).
However, I'm a bit worried about the separate concrete slabs—specifically about whether they'll expand at different rates and if filling the gaps might stress the LVP. Am I missing anything?
2 Answers
It's true that the separate slabs can expand and contract at different rates, which might create issues down the line. Make sure your concrete is flat and meets the manufacturer's installation specifications. Also, if there's moisture coming up through the concrete, consider using a dimple mat as an added precaution, especially for rigid core LVP.
Since your space is enclosed, leveling the concrete first is smart. I suggest laying down 1/2-inch tongue and groove plywood followed by 1/4-inch lauan to bring the floor height up and avoid any problems with the concrete settling unevenly. It’s a better long-term solution!