SFGate

Kaplan Architects, AIA One has to make sure there are no openings whatsoever around the house that they can get in. Make sure you install sturdy foundation vent grilles and keep them maintained. Make sure the eave ventilation is inspected periodically as well. Make sure all exterior doors are tight fitting and preferably weatherstripped. One can put a 2" layer of concrete 'ratproofing' in all crawl space areas under the house.

morticia9 Mice can enter through an opening the size of a nickel; just something to keep in mind.

Jefferson Park Collection Kaplan has the right idea. You need to make all the vents of heavy material (not the standard wire mesh). You can also have the vents fabricated to become an architecural element (cast bronze or linked bronze). Also, if you have a raised fondation, be sure to fill around every single hole that is cut through the floor for the plumbing or electrical etc. The photo is of a custom grill I made for a project in Santa Barbara.

Deborah Butler, Brickwood Builders Use a closed crawl space that has no vents and it also creates huge energy savings.

Brenda Fisher Mice do not like spray foamed walls nor the green blue jean fibre fill. The biggest thing though is not to attract them. Keep sheds and garden areas clean. Locate compost well away from the house as well as garbage areas. If you are building facilities for animals make sure feed is stored in contained areas or bins. Do not feed pets near the house.

designideas4me I would call vector control in the city or even an exterminator for ideas. I have had mice and they are the ones who tell you how to get rid of them.

Rebecca Cole Thank you so much. I am very grateful and would welcome more advice too.