I'm planning to install LVP in my kitchen and hallway this fall. I've got concrete subfloors in both areas, and I'm trying to figure out if I should go with a basic foam underlayment or splurge on something with better moisture protection. What's actually made a difference for you guys?
Concrete subfloors are moisture factories, especially in kitchens, so you really do need something with a vapor barrier - basic foam alone won't cut it and you'll end up with buckling planks in a couple years. I'd go with a thicker underlayment (around 3mm) that has built-in moisture protection, like the rubber-based or cork options; they cost more upfront but beat ripping everything out later because moisture got trapped underneath.
Moisture on concrete gets worse over time, not better, so if someone's already mentioned the vapor barrier issue they're spot on. What matters more than you'd think is actually the thickness and density of whatever you pick. Thinner foam underlayment compresses under foot traffic and loses its moisture-blocking ability faster, especially in a kitchen where you're walking on it constantly and maybe spilling water now and then.
For concrete specifically, aim for something at least 2mm thick with a built-in vapor barrier - not just a cheap foam layer. There are hybrid underlayments out there that combine foam with a polymer moisture barrier, and those tend to handle kitchen conditions way better than basic foam alone. The price difference isn't huge if you're only doing two rooms, and it saves you from tearing up buckling planks in eighteen months. You'll also want to check if your concrete is actually sealed or if water sits on it when it's wet; if water beads up, you might get away with something thinner, but if it soaks in, don't cheap out on protection.
LVP manufacturers usually void the warranty if you skip a moisture barrier on concrete, which tells you everything you need to know about how serious this is. I installed LVP in my kitchen last year with just basic foam and ended up with noticeable cupping within months - had to rip it all out and start over with a proper vapor barrier product. Now I use a closed-cell foam or cork underlayment with a built-in moisture barrier, and it's made all the difference. The extra cost upfront (maybe 30-40% more) is nothing compared to replacing buckled planks or dealing with mold underneath.
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