Ask Mr. Pest Control
Q. What would you recommend to prevent rodents from burrowing down into a crawlspace from the outside? If they have already done so, what is the best way to exclude them? I've heard of using screening in an L shape along the foundation as well as trenching gravel along the perimeter. — Jayce, WA
A. I don’t know that a gravel trench would keep rats from digging in and out of the crawlspace, but a curtain of hardware cloth should. Use 19-gauge hardware cloth or stronger with a ½ in. x ½ in. mesh or smaller. Attach it to the outside of the crawlspace and have it extend down two feet and out eight inches. The horizontal section is what keeps them from burrowing deeper. It’s better to install the hardware cloth after any rats living in the crawlspace have been removed.