I am getting ready to start a renovation on an old metal pole horse barn in southern California. 37 x 53. Currently it has a dirt floor inside. Instead of a concrete slab, I was considering building a wood floor foundation. (Foam Insulation covered in sand or gravel with PT sleepers or something like that) This is something I can do myself and will make running plumbing lines easier etc. Plus I think it will be considerably less expensive.

I have read some threads about this but am unsure as to vapor barriors, insulating, pest control, layout etc. Any other concerns I should be aware of?

Any comments or suggestions, positives and negatives as to why or why not go this route would be greatly appreciated. Thanks!