BN: Spraying foam in holes helps for a while but it turns to liquid and will eventually evaporate. Holes have to be sealed.

We did major extermination a few years ago. The result was great. We sealed holes on the bldg exterior on the ground floor. Once mice get into the bldg, they can go thru walls and get into any hole they find -- in apts and in bldg service areas.

We were painting all our bldg service areas anyway so when we removed all the equipment and supplies from the offices, trash areas, store rooms, etc., our exterminator sealed holes before we painted and put everything back in place. We also sealed holes in the compactor, boiler, oil tank and meter rooms. We were amazed at how many holes and wall fissures were found in those areas. We put metal sweeps on all service room doors (not rubber, mice can chew thru it) and got new trash bins with attached covers.

We sent residents a firm memo reminding them to discard trash properly and to seal holes in their apts. and we kept on top of this. We've had no complaints of mice/bugs since.

Interestingly, we also found that after we sealed all the holes in bldg service areas, the temperature on the ground floor was 8-10 degrees higher, so we've saved money on the cost of heating the lobby and the hallways to ground floor apts.

BN - You may not want to go as far as we did but I recommend your exterminator checking the bldg exterior for entry points and doing any common are interior work you can afford. People still have to seal holes to keep mice out of their apts, but anything you can do to keep mice out of the bldg, and inside the walls if they do get in, is worth the effort.