Building-science glossary for pest exclusion

Short answer

Twenty-one building terms that come up when we explain how pests get into Calgary homes, each in plain words with a link to the work that deals with it.

Air barrier · Vapour barrier · Rim joist · Sill plate · Soffit · Fascia · Flashing · Weep vent · Rain-screen · Penetration · Freeze-thaw cycle · Chinook · The 6 mm gap · Door sweep · Garage door bottom seal · Hardware cloth · Copper mesh · Harborage · Exclusion · Integrated pest management (IPM) · Crack injection

Air barrier: The layer that stops air moving through walls and ceilings. Gaps in it leak heat and can guide pests. See air sealing explainer.
Vapour barrier: A layer, often polyethylene on the warm side of Calgary walls, that limits moisture moving into the wall. See why moisture matters.
Rim joist: The framing board around the edge of a floor, sitting on the foundation. A common spot for gaps and penetrations. See mouse-proofing.
Sill plate: The board fastened on top of the foundation wall. The joint between sill and concrete often lets mice and ants in. See ant entry points.
Soffit: The underside of the roof overhang. Soffit returns and vented panels are common attic entry points. See mice in the attic.
Fascia: The board along the roof edge that the gutter attaches to. Gaps behind it lead into the soffit. See wasp prevention.
Flashing: Metal that sheds water where roofs meet walls. Gaps at flashing are a roofline entry point. See attic mouse work.
Weep vent: Small openings at the base of brick or stone that let water out. They need screens that keep pests out without blocking drainage. See brick and soffit entry.
Rain-screen: A gap behind cladding that lets walls drain and dry. Its open ends need pest screening. See exclusion engineering.
Penetration: Any hole through the envelope for pipes, cables, vents or meters. The most common entry points we close. See exclusion engineering.
Freeze-thaw cycle: Water freezing and thawing in a joint, which pushes it open over time. See exclusion vs extermination.
Chinook: A warm winter wind in southern Alberta that can thaw and refreeze a wall several times in one winter. See building envelope science.
The 6 mm gap: About the smallest gap a house mouse can fit through, per Penn State Extension. See mouse-proofing.
Door sweep: A strip on the bottom of a door that closes the gap to the floor. See mouse-proofing.
Garage door bottom seal: The rubber or vinyl strip on the bottom of a garage door. We refer its repair to garage-door partners. See garage: who fixes what.
Hardware cloth: Welded steel mesh used to screen vents and openings that must stay open. See exclusion engineering.
Copper mesh: Mesh packed into gaps so mice cannot chew through, usually finished with sealant. See mouse-proofing.
Harborage: Any place pests can hide and nest, such as clutter, insulation or wall voids. See structural assessment.
Exclusion: Closing the gaps pests use to get in, rather than only treating the pests. See exclusion vs extermination.
Integrated pest management (IPM): An approach that combines inspection, exclusion, sanitation and targeted treatment, using chemicals only where needed. See exclusion vs bait stations.
Crack injection: Filling foundation cracks with epoxy or polyurethane. A foundation trade; we refer it out. See ants and foundations.

Questions

What is a rim joist?

The framing board around the edge of a floor, sitting on the foundation. A common spot for gaps and penetrations.

What is a weep vent?

Small openings at the base of brick or stone that let water out. They need screens that keep pests out without blocking drainage.

How small a gap can a mouse use?

About 6 mm, according to Penn State Extension.

What does freeze-thaw do to sealant?

Water freezing and thawing in a joint, which pushes it open over time. Calgary’s Chinook swings can take a wall through several freeze-thaw cycles in one winter, and each cycle works sealant and trim joints loose.

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