Q: A friend of mine spent half a year dealing with a mouse infestation in her basement. Her situation was a total nightmare and makes me worry about mice or rats infesting my own home. What can I do to keep rodents out?

A: The Puget Sound attracts a lot of people with its natural beauty and climate, but it also attracts a variety of rodents. The unfortunate reality is that rats and mice are a constant threat to the structural integrity, health, and safety of our homes. Eliminating them or preventing their intrusion altogether should be a top priority for all homeowners.

Understanding the Threat

Rats naturally thrive in similar environments as humans; where humans go, rodents follow. This poses a serious threat to human health because rats and mice are known carriers of numerous transmittable diseases and hosts for disease-bearing insects and mites. Deer mice, for example, can transmit the deadly hantavirus.

As if the health threat wasn’t enough, rodent nesting habits are notorious for inflicting thousands of dollars in damage to homes. Whether they pull out and shred insulation and electrical wiring to create their homes or chew through roofing and siding material to file their teeth, nesting rodents can cause serious structural issues. Even your vehicle is vulnerable, as rats and mice have been known to burrow in ventilation systems and chew through vehicle upholstery and lines.

Luckily, there are many relatively inexpensive and unobtrusive preventative measures we can take to prevent rodents from invading in the first place.

Identification and Prevention

• Look for droppings, filth, or teeth marks. These signs of rodent presence might appear in hidden and enclosed areas of the home, such as cupboards and crawlspaces. Wiring, siding, or functional holes may also show signs of being gnawed, so keep an eye on exposed areas with these components.
• Keep an eye out for rodent nests. Rats and mice can shred up many different materials to create their nests. Common materials include paper or cloth, wood or insulation, and even leaves and branches from outside. Inspect dark, dry spaces in your home, especially attics, crawlspaces, and ceiling panels, for these amassed materials.
• Seal exterior entry points. A hole as small as a quarter inch in diameter is large enough for a mouse or rat to either squeeze through or gnaw wider to accommodate their size. Plugging holes in exterior siding, between roofing joints, and sealing decks or crawlspaces with materials like steel wool can go a long way in deterring rodent entry. Covering larger holes like vents, drainpipes, and chimneys with mesh or plastic sheeting can also help.
• Prevent trees and vines from growing too close. Rats and mice are expert climbers and jumpers. Don’t extend an invitation by allowing tree limbs or climbing ivy to grow too near the side of your roof. Once on the roof, rodents can easily find or make holes for themselves leading indoors.
• Properly store open food and seal trash. Cutting off exterior food and water sources significantly reduces rodents’ ability to thrive near or inside our homes—this includes pet food! Ensuring that pantry and pet food items are stored in hard plastic containers and that trash lids are tightly fitted will decrease scent triggers that attract rodents.

Kurt Treftz is co-founder of Cascade Pest Control, a member of the Master Builders Association of King and Snohomish Counties (MBAKS). If you have a home improvement, remodeling, or residential homebuilding question you’d like answered by one of MBAKS’ nearly 2,800 members, write to homework@mbaks.com.