I'm in the process of creating a mudroom. I live in a wet climate in western North Carolina. I wanted to go for a more natural ground insulation, so I chose perlite. Currently, I have 3 ½ inches of gravel against the ground. I was planning to put a little sand on top and then put a 6ml poly vapor barrier. Then, I was going to put on 3 inches of perlite and then an earthen subfloor that is mostly comprised of road base, clay slip, and lime. I was going to do a low moist mixture to tamp it and then allow it to dry fast.
I know that perlite can wick water, but what about pulling in moisture from the air. Will that be a problem if it's directly below the earthen subfloor and be able to grab moisture from the air through the earthen floor? Will it compromise the lime subfloor? FYI, eventually, I will put a finish earthen floor oiled and sealed on the top.
I guess I'm having a hard time imagining it to be a problem, since clay can absorb moisture from the air and we use that for plasters and such. In some ways, these earthen materials help to regulate the humidity in the air. Curious to hear any significant concerns if there are any.
Another option could be to put the perlite on top of the gravel and put the vapor barrier on top of the perlite, but I worry about the tamping and how that might create tears in the 6 ml plastic.