Concrete slab over dirt floor and best insulation for basement - California

Andy's Avatar (by Gravatar) by Andy in  Insulation 

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.



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Answer by

You'd only be adding to your problems in doing almost any of that. I'd only replace the ceiling insulation, face it with plastic sheeting and then simply fence it all. Attached to the bottom of the joists works perfectly and the rats can return without doing any damage.
Smaller spaced Cyclone fencing, 2x2 Concrete Mesh, Aluminum or Steel Siding/Roofing, Metal Slats or even Perforated Diamond Plate are all a lot cheaper, easier and best addressing...since none of those will crumble and break away.

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