Although you may think your home is relatively “tight,” in the typical home there are many openings where mice can enter. Generally, the older your home, the more openings and the more vulnerable you are to being invaded by mice. Young mice can squeeze under a door or through a crack and crevice only about 1/4-inch wide, about the width of a pencil. If the opening around a pipe or under a door isn’t quite big enough, mice will gnaw at it until they can fit through.

A hole chewed by a mouse is about 1-1/2 inches in diameter. The edges of a recently gnawed area will be light-colored and you may find small chewed pieces below. In general, the older the hole, the smoother and darker the edges since mice tend to gnaw off any rough edges around the opening over time. The oils in their fur gradually leave dark “rubmarks” as they pass through the hole.

These are some of the main entry points that mice use to get into a home:

1) Utility Lines – Mice squeeze into the narrow space around utility conduits and follow the line into a home. Underground electrical lines, gas lines, cable TV, telephone lines, and openings for water pipes all can provide a direct route from the outside to the inside. Likewise, above ground power lines and telephone lines provide access to roofs and attics. Openings where these conduits enter must be sealed.

2) Fireplaces – Once in an attic, mice may be able to get into the fireplace void by way of sheeting or metal collars that are improperly fitted. They can then get into the fireplace itself from the damper or from the cool and warm air returns. Mice can also get into the fireplace through cracks, missing mortar, or poorly fitted siding.

3) Garages – Mice can get into garages through open doors or under garage doors. Garage door thresholds rarely fit tightly enough to keep mice out. Once in the garage, mice can get into the house by following pipes, electrical lines, or furnace ducts.

4) Foundations, Floors, Walls, – Older buildings are especially susceptible to mice entering through cracked foundations, cracked plaster, deteriorated mortar joints, or warped siding. They can get into buildings with piers or shallow foundation walls by burrowing beneath the floor. Mice can also enter through gaps where exterior framing or siding meets the foundation. Mice can climb exterior walls and enter through bathroom vents, dryer vents, or gaps around window-installed air conditioning units.

Keeping mice out means caulking and sealing lots of openings, repairing and screening vents, replacing door thresholds, etc., etc. You can mouse-proof your home on your own, but as you can imagine, it’s time consuming. At Colonial, mouse exclusion is one of our specialties. Our trained experts know where to look for openings that would allow mouse entry. We use only the best materials and methods to mouse-proof your home. For more information on our mouse-proofing service, see our Rodent Control page under Services.