First confirm it's mice, not roof rats
Most Metro Vancouver homeowners who tell us they have mice actually have either juvenile Norway rats or roof rats. The diagnostic matters because the species drives the protocol. House mice are about 7-10 cm long body-only, light-grey to brown, with a tail roughly equal to body length. Their droppings are 3-6 mm long, pointed at one end, granular. Norway rat droppings are 18-20 mm, blunt, and capsule-shaped. Roof rat droppings are 12-15 mm and curved. If you find droppings consistently above eye level (in attic insulation, on shelves, on top of cabinets), it's almost certainly roof rats — read our companion article on telling them apart.
The five-stage protocol that actually works
House mouse elimination protocol — Metro Vancouver
The five-stage protocol every Wild Pest tech follows for a confirmed house mouse infestation in a Metro Vancouver home. Single-visit treatments fail because the entry points stay open; this is the only sequence that holds.
- 1Inspect the full perimeterWalk the exterior of the home with a flashlight at dusk. Check every utility penetration (water, gas, cable, dryer vent, A/C line), every door bottom and weatherproofing seam, every soffit-fascia junction, every crawlspace vent. House mice can fit through a 6 mm gap; mark every gap larger than that with painter's tape.
- 2Inspect the interior — kitchen, pantry, basement, atticInside, check under every appliance, behind toe-kicks, inside cabinets where pipes enter, attic edges, basement utility room corners. Look for droppings, gnaw marks on plastic or wood, and greasy 'rub marks' along baseboards. Tape-mark every interior gap larger than 6 mm.
- 3Seal exterior entry points with industrial materialStainless-steel mesh wool packed into utility penetrations, then closed-cell foam over the wool. Aluminum flashing and 19-gauge galvanised hardware cloth at vents. Replace soft weatherproofing with tighter-grade or door-bottom kits. Caulking alone fails — mice will chew through it within a season.
- 4Deploy tamper-resistant interior bait stationsPlace tamper-resistant rodent bait stations at every documented activity site, against walls (mice run along edges), spaced 3-5 metres apart. Use a multi-feeding anticoagulant (BC SGAR ban excludes brodifacoum and difethialone — first-generation anticoagulants like chlorophacinone are still legal). Indoor bait stations only — never exterior bait for residential single-family.
- 5Monitor and re-inspect at week 2, 4, and 6Re-inspect every two weeks for six weeks. Refresh bait, document new activity, seal any gaps missed in stage 3. By week 6, activity should be near zero. If you still see fresh droppings or smell ammonia, you missed an entry point — go back to stage 1.
What doesn't work (and why people keep doing it)
- Snap traps alone — fine for a single mouse spotted in a kitchen, useless against an established population. Mice reproduce faster than a homeowner can trap them.
- Ultrasonic repellers — Health Canada has reviewed these multiple times; the consensus is no measurable effect on rodent activity beyond placebo.
- Peppermint oil, cayenne, mothballs — short-term scent disturbances at best. Mice habituate within days. Mothballs are also a controlled pesticide and applying them indoors violates Health Canada labelling.
- Indoor-cat 'mouser' assumption — cats can suppress a single visiting mouse but cannot eliminate an established colony breeding inside walls.
- Sealing without baiting — if mice are already inside, sealing without suppression traps them indoors and they die in inaccessible voids, creating a smell problem that lasts weeks.
- Baiting without sealing — kills the current population but new mice recolonise from neighbouring properties within a few weeks.
When to call a pro vs DIY
Single mouse spotted, no other evidence: trap-and-clean DIY is reasonable. One snap trap per suspected entry, baited with peanut butter, checked daily. Multiple sightings, droppings in two or more rooms, sounds in walls, or activity in attic or crawlspace: book a professional inspection. The reason is not the trapping difficulty — it's the structural diagnosis. Most homeowners cannot identify all the entry points on a 1960s Burnaby ranch or a pre-war Vancouver craftsman without specialist tools (borescope, thermal camera, rooftop access). The exclusion is the permanent fix; the trapping is just the cleanup.
Why exclusion materials matter as much as placement
The material choice for sealing entry points determines whether the exclusion lasts 2 years or 20 years. Caulk alone on a utility penetration: rats chew through it in days when motivated. Steel wool alone: rusts in Metro Vancouver's wet climate, crumbles, and leaves the gap open again within 2-3 winters. The durable system: stainless-steel mesh wool packed tight into the gap, then closed-cell expanding foam sprayed over it. The foam keeps the wool in place and seals the perimeter; the wool provides the gnaw resistance. For larger openings (vent apertures), 19-gauge galvanised hardware cloth with quarter-inch mesh, screwed (not stapled) to the frame. This combination lasts 15-20 years in BC conditions. See the full materials guide in [how to rodent-proof your house](/guide/how-to-rodent-proof-your-house).
Mouse-proofing for specific Metro Vancouver housing types
Pre-war character homes (1910-1940s Kitsilano, Strathcona, East Van, New West): these homes have open crawlspaces with original wood-framed vents, knob-and-tube wiring chases that were never sealed when upgraded, and often a half-basement with original concrete that has cracked or settled. Entry-point density is the highest of any housing era. Budget for comprehensive perimeter work. Post-war ranchers (1950s-1970s, Burnaby, Delta, South Surrey): typically slab-on-grade with fewer crawlspace issues but aged utility penetrations at the slab perimeter, worn garage-door seals, and cedar-clad siding with gaps at corner boards. 1980s-1990s framed homes: generally fewer historic entry points but often have settling around slab penetrations and worn door sweeps. Condos and apartments: entry points are at the unit boundary — around pipe penetrations inside cabinets, HVAC supply and return voids, and ductwork chases. Mice travel between units through shared wall cavities and plumbing chases.