How Do Bats Get Into a House? Every Entry Point

Bats get into a house through gaps that already exist, not holes they make. They squeeze through openings as small as about 1 cm, roughly the width of a pen, along the roofline: soffit-fascia gaps, lifted shingles, unscreened vents, chimney flashing, and dormer joints. These spots sit high and out of sight, so a colony can move in unnoticed.

Unlike squirrels or raccoons, bats cannot chew, claw, or force their way in. They rely entirely on gaps your home already has. That is actually good news. It means the problem is about finding and sealing openings, not repairing major damage. Below, we walk through every common entry point, why such a tiny gap is enough, and how to spot the signs from the ground.

Why a bat needs only about 1 cm

A bat’s body is soft and flexible, with no rigid shoulders to block it. If a bat can fit its head through a gap, the rest of its body follows. For most bats in Ontario, including the little brown bat that so often roosts in attics, that means an opening of only about 1 to 1.5 cm, roughly the width of a pen or your thumb.

That is smaller than most homeowners ever picture. A gap that looks far too thin to matter is often exactly the kind of opening a bat uses every night. This is why entry points are so easy to miss, and why sealing your home against bats takes a careful, close-up look rather than a quick glance.

How do bats get into a house? The common entry points

Almost every bat entry point sits where two building materials meet, because those joints naturally leave small gaps as a house settles and ages. Here are the spots we find most often during inspections.

• Soffit-fascia gaps. The soffit is the underside of your roof overhang; the fascia is the board behind the gutter. Where they meet, gaps open up over time. This is one of the single most common ways bats get in.
• Roofline and ridge. Lifted or curled shingles near the peak, and gaps under the ridge cap, give bats a sheltered way into the attic right at the top of the house.
• Gable vents. These triangular vents high on the end walls let air into the attic. If the screening is torn, loose, or missing, they become an open door.
• Chimney and flashing. The metal flashing that seals a chimney to the roof often lifts at the edges. Bats slip into the gap behind it, and open or uncapped chimneys are an easy route too.
• Dormer joints. Anywhere a dormer window meets the main roof creates corners and seams. These joints are a classic hiding spot for small colonies.
• Utility penetrations. Wherever pipes, wires, cables, or vents pass through the wall or roof, the gap around them is rarely sealed tightly.
• Loose or damaged vents. Attic vents, roof vents, and exhaust vents with bent louvres or failed screens give bats a way straight inside.

It helps to understand why these gaps appear in the first place. Soffit gaps often form as a house settles and the wood expands and contracts through Ontario’s freeze-thaw winters, slowly pulling the soffit panel away from the fascia board until a finger-width gap opens along the run. Gable-vent screens fail for a similar reason: the mesh is usually thin aluminum or plastic that corrodes, tears, or works loose at the staples over the years, leaving a wide, sheltered opening right into the warmest part of the attic. Chimney flashing lifts as the sealant behind it dries and cracks. None of these are signs of a poorly built home. They are the normal wear that every roof develops, and they are exactly the openings a bat is built to exploit.

Because all of these sit high on the house and are small, a colony can settle in for months before you spot droppings or hear scratching. If you are trying to work out whether the bats are in the attic itself or tucked inside a wall cavity, our guide to bats in walls vs attic explains how the two differ and why it matters for the fix.

Where do colonies sneak in?

A single bat and a maternity colony often use the same kinds of gaps, but colonies favour spots that are warm, sheltered, and stable. Attics are ideal because they hold heat and stay undisturbed. The most common colony entries are the soffit-fascia line and the ridge, since both run the length of the roof and offer many small openings along the way.

Colonies also tend to reuse the same entry year after year. That repeated traffic leaves telltale signs, which is exactly what an inspection looks for.

Entry point	How common	How visible from the ground
Soffit-fascia gap	Very common	Hard — needs binoculars or a close look
Roofline / ridge	Very common	Hard — high and near the peak
Gable vents	Common	Moderate — visible but detail is tricky
Chimney flashing	Common	Hard — often hidden behind the chimney
Dormer joints	Common	Moderate — corners can be scanned
Utility penetrations	Occasional	Moderate — lower and easier to see
Loose vents	Occasional	Moderate — depends on placement

How to inspect from the ground

You do not need to climb a ladder to start narrowing down where bats are getting in. A careful look from the ground tells you a lot, and it helps a professional focus the inspection.

1. Scan the roofline with binoculars. Slowly work along the soffit-fascia line, the ridge, the gable vents, and the chimney, the four spots bats favour most.
2. Look for brown staining. Bats leave dark, oily streaks around a gap they use often, from the oils in their fur. The staining is usually concentrated at one specific opening rather than spread evenly.
3. Check for droppings. Small, dark, crumbly droppings collecting on the siding, a window ledge, or the ground point to an active entry above.
4. Listen at dawn and dusk. A settled colony can be faintly audible from inside — light scratching or chittering in the attic or wall as the bats leave to feed and return.
5. Watch at dusk. On a warm evening, bats stream out to hunt. You may see them emerge from one specific gap, which pinpoints the entry.

These clues narrow things down, but the gaps themselves are small and high, and the freshest staining is easy to confuse with ordinary weathering when you are looking up from the yard.

Finding entries is exactly what an inspection does

If all of this feels like a lot to track down, that is completely normal, and it is the whole point of a professional inspection. Finding every active entry point is the core of the job. We check the roofline up close, confirm which gaps bats are actually using, and map out a plan before anything is sealed.

That last part matters. Bat removal is not about trapping or harming the animals. It is about installing one-way doors at the active entries so bats can leave to feed but cannot get back in, then sealing every gap once they are out. If you want the full picture of how that works, our exclusion vs removal guide breaks down the difference, and our complete bat-proofing guide covers how each entry point gets sealed for good.

Bats are also a protected species in Ontario, which shapes how and when the work can be done. Our humane bat removal complete guide walks through what the law means for homeowners here.

What happens after we find the entries

Finding the gaps is only the first half of the job. Once we confirm which entries are active, we fit one-way doors over them. These are lightweight devices that let a bat crawl out to feed at night but block it from crawling back in. The bats leave on their own, on their own schedule, with no trapping and no handling.

We leave the one-way doors in place for several days to make sure every bat has cleared out, then remove them and seal each opening properly with materials matched to your roofline. Only once the colony is fully out do we close the gaps for good. Sealing too early is the single biggest mistake, because a bat shut inside will hunt for another way out, sometimes deeper into the living space rather than back outdoors.

This is also why prompt exclusion matters once the season allows it. The longer a colony stays, the more droppings, known as guano, build up in the attic, along with a musky odour that can slowly work its way into the rooms below. Acting within the exclusion window keeps that buildup to a minimum and closes the door before the next spring’s colony returns to the same warm, familiar spot.

Seasonal timing: when entries can be sealed

Timing is everything with bat exclusion. From roughly May to early August is maternity season, when female bats raise flightless pups in the roost. Sealing entry points then can trap young bats inside, which is inhumane, illegal for a protected species, and leads to odour and damage as they cannot get out. So during those months we do not seal.

The practical exclusion window in Ontario is mid-August through October, once the pups can fly and before bats settle in for winter. If you discover bats during maternity season, the right move is not to wait and hope. Book the inspection now, hold your spot, and we complete the exclusion the moment the season opens. Our guide to maternity season timing explains exactly why this window matters.

What does it cost to seal bats out?

There is no single figure, because the price depends on the specifics: how many active entry points there are, how extensive the job is, how easy the roofline is to reach, and whether any cleanup is needed. After we look at your home during the free inspection, we give you a clear, honest quote up front and walk you through it so there are no surprises.

Book a free inspection

If you think bats are getting into your house, the first step is simply to find out for sure. We offer a free, no-obligation inspection across Grey, Bruce, Simcoe and Huron counties, and every exclusion we do is backed by a transferable Lifetime Warranty: if a bat ever gets back in through a point we sealed, we return and fix it at no charge, for as long as you own the home.

You can request your inspection through our bat removal and exclusion service page or the home page. We will find every entry point, plan a humane exclusion, and seal your home so the bats stay outside where they belong.