Foundation – Can Thin Concrete Slab Prevent Rodent Intrusion in Crawl Space?

Personally I would just fill the holes with dirt, why does it need to be more complicated than that? Concrete isn't going to stop them any more than dirt, since presumably the yard is mostly dirt anyway.

Rat mites consume blood. They may be choosy about who they bite and not everyone has an allergic reaction to the bite.

This part may be unnecessary but I took everything out of my room and put it in the garage. I put the items in sealed contractor bags with a nuvan strip each. I hung a nuvan strip in the garage. I washed the floor, wall edges, all the nooks around the windows, and the crevices around the room with diluted pinesol.

I used boric acid along the edge of walls and in the bottom of dressers. To my knowledge, boric acid kills roaches either by being consumed and destroying their stomach bacteria or on contact by cutting open their exoskeleton (like what diatomaceous earth does). So for the latter reason it might have an effect on the mites. But it's not worth counting on.

For assurance, I sprayed Lysol around the edge of the walls and that kills the mites on contact.

I set a peanut butter rat trap in the crawl space. Several hours later I heard squeaking. There was one live and one dead rat trapped. I sprayed the area with Spectracide Bug Stop and got rid of the rats. I set a new trap and expect there are more rats.

I got 1/4" hardware cloth and I'm going to patch the broken foundation screens around the house. There's also two air vents that need to be screened to prevent further problems with birds/rodents.

The mites are a symptom of the rat problem. Once the rodents are controlled, the mites should dissipate.