Get Out and Stay Out

Features - Urban Wildlife Exclusion

Exclusion tips for rodents and wildlife.

November 7, 2022

House: © Bet_Noire | AdobeStock; Rat: Envato Elements

The most effective and humane way to prevent rodent and wildlife issues is to keep them out of structures in the first place.

This can be done with exclusion — the process of sealing up all those places where critters might enter a home or business and cause a nuisance. It’s a permanent solution for which clients are willing to pay. As such more pest management professionals are offering exclusion or pest-proofing as an add-on service. Successful exclusion relies on performing thorough inspections. Here are 14 places to examine, plus tips for fixing any gaps, cracks, holes or vulnerabilities you might find:

Wooden doors. Rats will gnaw through and under wooden doors. Install galvanized 24-gauge iron flashing around the bottom of the door, door sills and jambs.

PIPE GAPS. Openings where pipes and utility lines pass through walls are a common entry point. Use galvanized 24-gauge iron flashing to close gaps in wood siding. For brick, stone or cement walls, use bricks, cement or an appropriate high-grade sealant (not caulking compound). Cover the sealed space around the pipes with escutcheon plates.

VENTS. Vents provide easy access to attics and crawlspaces, even clothes dryers and bathrooms. Cover vents with 18-gauge ½-inch-thick mesh, galvanized expanded metal or 16-gauge ½-inch-thick galvanized mesh wire cloth. Protect low windows with 19-gauge, ½-inch-thick galvanized wire cloth.

ROOFLINE AND CORNERS. Areas where the shingles meet soffits or where edges end in corners should be inspected. Bats can enter through 3/8-inch gaps. To close small holes and gaps, use ¼-inch hardware cloth or sheet metal. Depending on the critter, softer aluminum flashing, insulation foam, particle board and plywood can be used. (Bats, for instance, won’t chew through these materials but rats and squirrels will.)

CHIMNEYS. A chimney without a cap or bad flashing offers easy points of entry. Install a chimney screen and repair flashing.

EAVES. Eaves and soffits are easily penetrated by critters, especially if they’ve sustained previous damage from water or wind. Sheet metal or mesh hardware cloth (¼ or ½ inch) can be fastened over areas of eaves on wood buildings. Plastic or nylon netting can discourage birds.

DECKS, PORCHES, SHEDS & MORE. Skunks and possums find refuge under decks, sheds, porches, stairs, mobile homes and other raised structures. Screen off these areas with ½-inch wire mesh fencing. To discourage critters from burrowing under the fencing, bury it 12 to 18 inches below ground with 6-plus inches extending outward horizontally.

SIDEWALK GRATES. Metal grates may cover storm drain culverts or building exhaust vents. They’re also a potential entry point for pests. Close them with 18-gauge ½-inch-thick mesh or galvanized expanded metal.

HOLLOW WALL OPENINGS. Openings into hollow walls, particularly between the floor and floor sills, should be closed with 19-gauge, ½-inch-thick mesh, galvanized wire cloth, or galvanized 24-gauge sheet iron.

DEFECTIVE DRAINS. Rats often travel inside defective or non-functioning drainpipes, or they’ll burrow along such pipes, right into a building. Cement a metal cover with small perforations over the drainpipe in the floor. Patch openings around the drain where it enters the building with cement mortar.

LARGE SIDEWALK CRACKS. Rats will enter cracks between the sidewalk and building exterior, exploring the foundation walls for breaches. Seal cracks with cement or high-quality exterior-grade sealant.

VERTICAL PIPES. Critters can travel up vertical drainpipes, pipe vents and wires to gain access to the roof or upper stories. Place a circular, galvanized metal guard around vertical utilities to prevent them from climbing up.

OVERHANGING BRANCHES. Rodents and wildlife use overhanging tree limbs to get on the roof. Prune branches back a minimum of 6 feet.

THE CRAWL WALL. In structures with crawlspaces (no basement), critters may burrow beneath the foundation wall. To prevent this, install a curtain wall or barrier of corrugated 29-gauge metal sheeting or concrete around the foundation wall about 2 feet below ground with an 8-inch L-shaped flange directed away from the building.

Remember, structures located in areas with high rodent and wildlife pressure (such as near creeks, fields, abandoned lots, infested streets) require monthly inspections to ensure the structure has not deteriorated in places due to storms, wear and tear or construction. PMPs should also inspect to make sure that animals have not made new breaches.

Editor’s Note: This story first appeared in the Fall 2020 issue of PCT Canada. The source is “The Mallis Handbook of Pest Control.”