7 Ways to Block Mice, Spiders, and Stink Bugs Before They Move in This Fall

A juvenile mouse can squeeze through a gap the width of a #2 pencil, roughly 6 millimetres. That means the tiny crack under your back door, the gap where the dryer vent meets the wall, and the forgotten vent screen in your crawlspace are all open invitations once temperatures drop in September.

Start at the Foundation, Work Up

Walk the perimeter of your house with a tube of exterior-grade polyurethane caulk and a headlamp. Focus on where different materials meet: siding and foundation, window frames and brick, anywhere a pipe or conduit enters the wall. Steel wool jammed into larger gaps before caulking creates a barrier rodents cannot chew through. Use copper mesh for the largest openings, as it won't rust out over a wet BC winter.

Screen Every Vent, Including the Ones You Forgot About

Your bathroom fan vent, kitchen range hood, and dryer exhaust are thermal beacons in October. Pests detect heat gradients from several metres away. Install 1/4 inch galvanized hardware cloth over every exterior vent opening. Do not use plastic mesh. Rats chew through it in under an hour. Check your roof vents and soffit vents while you're at it, the Western Conifer Seed Bug, often mistaken for a cockroach, enters homes almost exclusively through soffit gaps.

Cut Back Branches Within Two Metres of the Roofline

Roof Rats, common in Metro Vancouver's older neighbourhoods, travel along overhanging branches like highways. A maple branch touching your eaves in summer becomes a direct route to your attic once the leaves drop and food sources disappear. Trim everything back to at least a 3-foot clearance. If you're near the Port of Vancouver or along the Fraser River corridor, this is non-negotiable, rodent pressure in those areas is year-round, and it intensifies the moment garden vegetables stop producing.

Replace Damaged Weather Stripping Before the First Frost

The rubber seal at the bottom of your garage door compresses and cracks after two or three years of UV exposure. A gap as small as 6mm there is enough for a full-grown House Mouse. Check every exterior door. Lift the bottom edge of the weather stripping and look for light. If you see daylight, so does everything outside. Replacement stripping costs $40 and installs in under twenty minutes with a utility knife and a stapler.

Clean Your Gutters and Downspouts in Late September

This isn't aesthetic. Clogged gutters hold standing water and decomposing leaf matter, which attracts insects, which attract spiders, which then migrate indoors when the first overnight frost hits. More importantly, overflowing gutters saturate the soil around your foundation. That drives ground-level pests, particularly spiders and centipedes, up the exterior wall and into any crack they can find. Once inside insulation or behind drywall, pheromone trails can attract future infestations for years.

Move Firewood at Least 20 Feet From the House

A woodpile stacked against your foundation is a heated, sheltered staging ground. Mice nest in it. Spiders hunt in it. Stink bugs overwinter in the bark. When you carry a log inside in December, you're carrying passengers. Stack firewood on a raised rack, at least 20 feet away from the house, and only bring in what you'll burn that day.

Skip the Bird Feeder Until January

Feeding birds in the fall means feeding rats. Sunflower seeds and suet that hit the ground don't disappear, they draw rodents to your yard, and once they're there, they start looking for ways in. If you must feed birds, use a tray feeder with a catch basin and clean up daily. Better: wait until after the first hard freeze when natural food sources are actually gone.

The one most people skip is the vent screening. It's the highest-leverage fix, $30 in hardware cloth eliminates the route that accounts for the majority of fall entries.