I have a basement/crawl space with a dirt floor (California, Zone 3, 1920s wooden frame house). Two questions:
1) I'd like to cover the dirt floor with concrete. Do I need to put in a layer of gravel and a vapor barrier first? Even though its California the basement has some damp issues because it's on the side of a hill. We have a French drain around the house perimeter to stop the worst water seepage.
2) We currently have fiberglass batten insulation in the basement ceiling but it is rat contaminated and needs to be removed (yuk). I'm wondering if it would make more sense to insulate the basement walls rather than the ceiling since we are starting over, and am leaning towards closed cell foam insulation in the shear walls (the basement is earthquake retrofitted with shear walls). Any feedback on that? I'm looking for insulation that is effective and less appealing to rats (we are doing a rodent exclusion project as well but I am assuming you can never completely keep rodents out). I'm especially interested in comments from people who have done insulation combined with earthquake retrofits as it raises its own issues.