I would totally stay away from limestone. I can't say for sure that it would be bad but I'm fairly certain it might. When I was a chef we used to use limestone to line the bottom of containers holding stuff that needed to be kept dry. The limestone was supposed to be the part of the equation that helped keep the moisture out. Now I don't know if it would drastically reduce the moisture but I'd at least look into it before hand. Good luck, and let me know what you find.