Squirrels in the Attic: What to Do When They Move In for Winter

Quick answer: Daytime scampering overhead is almost always squirrels; night-time scratching in walls is almost always mice. Fall is peak attic-entry season in Ontario because second litters are being raised and adults are choosing winter dens at the same time. Trapping and driving the animal away does not work — Ontario law requires release within one kilometre of capture, and a squirrel released that close simply returns to the hole it knows. The only durable fix is one-way exclusion plus sealing every entry point, done in the right order.

There’s a specific week every fall — usually between late September and mid-October, depending how far north you are — when the calls change. All summer it’s wasps. Then, almost overnight, it’s “something is running around above my bedroom ceiling.”

That’s squirrel season, and two things drive it.

Why fall is when they move in

Second litters. Grey and red squirrels in Ontario typically produce two litters a year — one in late winter, one in mid to late summer. The late-summer young are becoming independent right now. They need somewhere to overwinter, and they aren’t going back to mum’s drey.

Winter den selection. Squirrels don’t hibernate; they ride out cold snaps in an insulated den and live off cached food. An outdoor leaf nest works in July. It’s a poor place to spend a February night in Barrie or Orillia. A dry, insulated, predator-free attic well above freezing is, from a squirrel’s point of view, the best real estate in the neighbourhood.

Together, that’s a short, intense window where newly independent animals are actively shopping for winter dens. It’s open right now.

Is it squirrels, or is it mice?

Before anything else, identify what you actually have — because the response is completely different and the wrong one wastes weeks.

Timing is the most reliable tell. Squirrels are diurnal — loudest shortly after sunrise and again in the late afternoon, with a quiet stretch midday. Mice and rats are nocturnal, busiest between roughly 10 p.m. and 3 a.m.

Sound character is the second. Squirrels are heavy: distinct rolling, scampering, and sometimes an audible thump as nuts or cones get dragged and dropped. People describe it as “someone bowling up there.” Mice produce a faster, finer scratching or gnawing, usually inside a wall cavity rather than across a ceiling.

Location. Squirrels occupy open attic space and soffits. Mice are in wall voids, under insulation, behind cabinets, along the sill plate.

If the pattern points to rodents, that’s a different playbook — start with our house mouse identification page and our guide to whether mice need an exterminator. Squirrel identification detail is on our squirrels library page.

How they get in (and it’s rarely dramatic)

Squirrels are climbers with continuously growing incisors and patience. A gap doesn’t need to be squirrel-sized to start with — it needs to be chewable.

The standard entry points, roughly in order of frequency:

• Roof–soffit intersections. Where a lower roofline meets the wall there’s frequently a gap behind the soffit return — invisible from the ground, and the most common entry we find.
• Roof and turbine vents. Plastic louvre vents chew through easily; aluminium ones get pried at the flange.
• Gable and attic vents with screening that’s degraded or was never properly fastened.
• Fascia gaps, especially where fascia has cupped or pulled away from the rafter tails.
• Chimney chases, plumbing stacks, and bathroom fan vents with a cracked roof boot.
• Overhanging branches. Squirrels routinely jump two to three metres horizontally. A branch ending three metres from your roof is still a launch pad.

Worth stressing: a squirrel doesn’t need a hole to find a hole. It patrols the roofline, tests seams, and works at the weak one. That’s why “we sealed the hole they were using and they came back somewhere else” is such a common story — the animal already knew about the second route.

Why trap-and-relocate is the wrong answer in Ontario

This is where most DIY attempts go sideways, and where Ontario’s rules differ meaningfully from the American advice that dominates search results.

Under Ontario’s Fish and Wildlife Conservation Act, wildlife captured as a nuisance animal must be released within one kilometre of where it was caught, and within 24 hours. There are specific provisions and exemptions — confirm the current requirements with the Ministry before setting anything — but the one-kilometre principle is the part that matters practically.

A squirrel released one kilometre from your house knows exactly where your attic is, has a well-established route back, and will be at the entry point before you’ve finished putting the trap away. Relocation “works” only in the sense that the homeowner watches the animal leave.

Driving it farther isn’t a workaround — it’s against the rules, and it doesn’t work either. A squirrel dropped into unfamiliar territory in late fall has no cached food, no den and no standing in the local hierarchy; survival rates are poor. It trades your problem for the animal’s, and you still have the hole.

The timing issue nobody mentions: in early fall there may still be dependent young up there. Remove the adult, seal the entry, and you’ve walled in a litter — an odour problem inside a wall cavity within a week, and a far more invasive repair than the one you were avoiding. Any competent fall attic job checks for young before anything is sealed.

What actually resolves it: exclusion, in order

The method that works is unglamorous and sequential. Skip a step and you redo the whole thing.

1. Full exterior inspection. Every roofline, vent, soffit return, fascia join and penetration — not just where you hear noise. The goal is a complete map of active and potential entries.

2. Attic interior assessment. Confirm the species, look for young, assess damage. Chewed wiring insulation is the reason this isn’t purely a nuisance issue.

3. Seal every entry except one. Secondary routes get closed with materials the animal can’t chew through — heavy-gauge mesh and metal flashing, properly fastened. Foam and caulk alone are decorative on a squirrel job.

4. One-way door on the primary entry. The animal exits normally and can’t re-enter, leaving on its own schedule — which is what keeps young from being separated from an adult.

5. Remove the device and seal the last hole, only after confirming the attic is clear.

6. Clean-up and, where warranted, insulation remediation. Latrine areas and damaged insulation cost you R-value and hold odour that draws the next animal to the same spot.

7. Trim back the runway. Branches cut to roughly three metres from the roofline — the step homeowners most often decline and most often regret.

The scope of our wildlife work is on the wildlife removal page; we cover it across Simcoe County and Durham, including Pickering and Ajax.

What it costs, and the part worth thinking about

Attic wildlife work is quoted after inspection rather than off a price list, because the variables are real — roof height and pitch, number of entry points, whether young are present, how much insulation damage has happened. A single soffit return on a bungalow and a three-storey roofline with four active entries are not the same job.

Every job starts with a $95 professional inspection, credited when you book the treatment. That inspection produces the entry-point map and a fixed quote before any work begins.

Here’s the piece worth sitting with. Sealing a squirrel out in October closes a set of gaps in your building envelope — and those same gaps, the soffit returns and vent screening and fascia joins, are the routes mice use through November and December. It’s genuinely common for a household to resolve a squirrel problem in the fall and call about scratching in the walls eight weeks later, having never connected the two.

That’s why the recommended path isn’t a one-time job on its own. The Complete Mice Protection plan at $895 per year keeps the rodent side of that same envelope monitored through the whole cold season, on scheduled visits rather than reactive callouts. The Essentials plan at $1,195 covers both the rodent and insect pressure a year puts on the structure.

Run the numbers as you would on anything else: a one-time exclusion job, plus a separate mouse treatment, plus insulation remediation in a bad year — against one annual plan where the envelope stays sealed and monitored. The one-time service deals with the animal in your attic this week. The plan is what stops you doing this again next October.

Not sure what you need? Take the free quote quiz or see Plans & Pricing.

Call (705) 302-1887 to book an inspection. Sani IQ is BBB Accredited with a 5.0 rating across 126 Google reviews, carries $5M liability coverage, and is licensed under the Ontario Pesticides Act and registered with the MECP. Every technician is employed, licensed and background-checked.

Frequently asked questions

How do I know if it’s squirrels or mice in my attic? Time of day is the fastest test. Squirrels are active at dawn and late afternoon and go quiet overnight; mice are busiest after midnight. Squirrels also sound heavy and produce rolling or thumping noises across the ceiling, while mice produce finer scratching inside walls.

Can I just put mothballs or a radio up there to drive them out? No. Repellents have a poor track record with squirrels, and a determined animal habituates within days. Worse, a half-effective repellent can push one deeper into the structure — into a wall cavity or soffit run — where it’s harder to remove and more likely to die somewhere inaccessible.

Is it legal to trap a squirrel on my own property in Ontario? There are provisions allowing a property owner to deal with nuisance wildlife, but they carry requirements — including release within one kilometre of the capture site within 24 hours. Confirm the current rules with the Ministry before setting a trap. In practice, that one-kilometre rule is exactly why trapping rarely solves the problem.

What damage do squirrels actually do? The serious one is chewed electrical wiring. Beyond that: compressed and soiled insulation that costs you on heating, chewed vent components and structural wood, and stored belongings. It accumulates quietly — which is why a noise you’ve been ignoring since October is worth investigating.

Will they leave on their own in the spring? Some individuals move out as it warms. But an attic that housed a squirrel over winter is a proven den site and tends to get reused — by the same animal, its offspring, or the next squirrel that finds the open route. The hole is the problem, not the occupant.

There’s a smell in the attic and the noise stopped. What now? Call. That combination usually means an animal has died inside the structure, and locating it before it becomes a longer-term odour and insect problem is time-sensitive. Reach us at (705) 302-1887.