I would set a bunch, and I mean a bunch of glue traps along the walls and baseboards of the house. Rats don't like the open and travel mainly along the walls for protection. Use a length of fishing line, preferably braided, not monofilament, attached to the glue traps so you can pull them out as needed without crawling under the home. Rats are afraid of anything new so you might want to put them out for a few days before exposing the glue. I would put out a dozen or so glue traps on say Monday and on Friday, go back and expose the glue. After the weekend, I'd pull them all out replace them with new and dispose of your catch. Repeat as necessary. You won't 'scare' them out ! Mothballs and peppermint won't work...and if there are babies under there, nothing short of catching them will get rid of them. They will protect their young....good luck...Dennis