You better tear down the whole foundation and slab and start fresh.
I'm just kiddin, you don't need that for San Diego
It is a constant 70 degrees out there. Your part of the country is usually only a slab on grade anyway. Exept for an occasional varmint gettin under there, I wouldn't worry to much.
If your concerned check with your local building official for more specifics for your area. They will be the ones to tell you what you can get by with anyway.
You guys are sooooo lucky.