Walk the foundation
Start at ground level, where Norway rats enter. Check every crawl space vent screen; older screens rust in Seattle's damp air and can crumble. Replace damaged screens with quarter-inch galvanized hardware cloth, which keeps airflow while blocking rodents.
Look at pipe, gas and cable entry points. The drilled hole is often larger than the pipe, leaving a crescent gap. Fill gaps with steel mesh or copper mesh and finish with a sealant. Foam alone can be chewed through.
Check the roofline and garage
Roof rats come in high. Look where rooflines meet, where gutters meet fascia, and at gable vents. Trim branches back so they are not touching or overhanging the roof.
Garage doors are a common entry. Check the bottom seal and the corners where the door meets the slab. Replace chewed weatherstripping and add corner seals if light shows through.
Remove food and shelter
Move pet food, bird seed and bulk food into hard sealed containers. Clean up fallen fruit and bird seed under feeders. Keep garbage and compost lids closed.
Clear woodpiles, stored lumber and dense debris away from the foundation. Rodents use cover to approach the house unseen.
Inside the house
Indoors, focus on the kitchen and utility areas. Pull the stove and fridge out if you can and look for gaps where pipes and cables enter. Check under sinks for openings around supply and drain lines. Seal small gaps with steel wool and sealant.
Store holiday decorations and boxes in sealed plastic tubs rather than cardboard. Cardboard is easy nesting material and hides droppings. Keep stored items off the floor in garages and basements so you can see along walls.
Finally, check your dryer vent flap and bathroom fan vents outside. Flaps that stick open or have missing louvers are an easy route in. Vent guards keep airflow working while blocking rodents and birds.
Set an early warning
Place a few snap traps in the garage and along crawl space entry routes before the season starts. Early captures tell you rodents are testing the house.
If you find fresh droppings, gnawing or grease marks, deal with it early. A quiet house in October is far easier to keep quiet than a house with a nest by December.
What to do if rodents are already inside
If you already see fresh droppings, hear scratching at night or find gnawed food, sealing alone is not enough. Sealing a house with rodents inside can trap them in walls, where they chew new routes or die and cause odor problems.
The right order is to remove the animals first with well-placed snap traps along runways, then seal entry points once activity stops. Check traps daily and wear gloves when handling them.
Clean up droppings carefully. Wet them with a disinfectant, wait a few minutes, then wipe up with paper towels while wearing gloves. Never sweep or vacuum dry droppings, because that can put harmful particles into the air.
If activity continues after a week or two of trapping, there is usually an open entry you have not found. That is the point where a professional inspection of the crawl space, attic and roofline pays for itself.
The fall checklist
- Replace rusted crawl vent screens with quarter-inch hardware cloth
- Seal pipe and cable gaps with steel mesh and sealant
- Install door sweeps and garage corner seals
- Trim branches back from the roofline
- Store food, pet food and seed in sealed containers
- Close garbage and compost lids
- Move woodpiles away from the foundation
- Set a few early-warning snap traps in the garage