We've done that in the past, and it is such a racket. "That'll be ____ hundred dollars for us to put down the chemicals. And we don't get up on a ladder and stuff steel wool into every single crack bigger than a 1/4" wide--you do."

We had bat-proofed the house years ago, and got rid of them after an epic struggle.

And then we had the house re-roofed. Which, of course, opened up all sorts of cracks again. Yeesh.