How are they getting in? Your best remedy is to block access from the outside.

When we had mice in the crawlspace under a house I once lived in, we used moth balls to drive them out. I was pleasantly surprised at how fast they left, and that we really couldn't smell the moth balls in the house (only the occasional whiff).

Once they are gone though, you do need to block their reentry like snookums2 says. It's the only way to permanently get rid of them.

find the entry points & seal them off with metal flashing.
caulk flashing in place & screw down flashing.

if you are going to seal, make sure that you
use materials that will last & mice can't eat through.

btw..moth balls & pets are a bad combo.

we have just had our first cold night...and don't
you know...I saw a mouse about 3:00 this morning.
my dog was just going crazy barking at it...but
she didn't attempt to catch it!

best of luck.

The only way to rid a crawlspace of rats/etc. is to permanently seal your entire foundation, exterior walls, and roof. ANY and ALL points of entry, no matter how small, must be repaired, filled, and sealed. Any overhanging branches from trees must be trimmed back so they do not touch your roof. Yes, it can be expensive, but do you really want to deal with a rodent problem or risk poisoning your pets?

Our house was built in 1910. We had a similar problem. A rat died inside one of our walls, and the smell was HORRIBLE. We couldn't find it so we had to wait out the smell, which took a couple of weeks.We hired our exterminator to dig a 12" deep 12" wide trench around the entire perimeter of our foundation. It was then filled with concrete. ALL possible points of entry on the exterior of the house were repaired. This was completed in January 2013 and, knock on wood, we have not had any more problems with rats, squirrels, or chipmunks.

I wish you good luck with solving your problem.

We're in an older home and have experienced mice, esp during change of seasons. It's often not that easy to find the entry point, there are so many nooks and crannies and unlevel areas that small critters can access. Moth balls worked for us; I placed it behind the stove so our pup could not get to it. Also, I've read, pure oils, like peppermint work. i had my kitchen floor and ceiling joists leveled and after the drywall was installed, I had them fill the floor and ceiling where they meet the walls completely filled with filler spray. Around areas like plumbing coming up thru the floor, I had fine steel wool put completely around the hole opening around the pipes. I hope it all works - I've been known to jump on a chair when seeing a critter.

we live in a house that is only 15 years old and have battled mice in the attic (and possibly squirrels ) for years. i finally gave in and called a reputable pest control company that seals up all entry points. many of the others just put out bait which isn't the solution i wanted.
it was expensive but if they had destroyed our insulation in the attic, that would have been more costly to replace.
good luck!

A big thanks to everyone who replied and made suggestions! Sorry for the delay in responding, I had the flu last week and was mostly prone on the sofa.

I agree that getting all of the nooks and crannies closed is the ultimate solution. I know of two spots right now where they can get in. Plus, they tunnel which makes them even sneakier. Demo started yesterday, so a tight house will be tough for the next couple of months. I hope all of the racket will make them want a new home.

I'm adding closing up all of the gaps to the list to be addressed during the construction!

Again, THANKS!