How Bats Get Into the Living Space of Your Home
Finding a bat inside your bedroom, basement, bathroom, kitchen, or living room can be alarming. Most homeowners assume the bat flew in through an open door or window. It didn’t.
Never happened.
Even if you think it did, having a bat fly thru an open door or window would still means you have bats. It wasn’t random. Which we explain in a different article here.
Every homeowner will dismiss the first bat encountered inside as a fluke. It usually takes a few more “fluke” before they are willing to believe otherwise. However, when bats are found inside, they did not come directly from outside into your living space. It came from somewhere inside the structure.
Bats enter homes through rooflines, soffits, chimneys, fascia gaps, vents, siding, or other exterior openings. Once inside, they can move through attics, wall cavities, chimney chases, basement ceilings, furnace rooms, and other hidden spaces.
From there, a lost bat can eventually find its way into the living space.
The Bat Are Already Inside the Structure
A house is not one solid sealed box.
Behind the finished walls and ceilings are hidden spaces: attics, wall cavities, plumbing gaps, wiring openings, chimney chases, furnace rooms, dropped ceilings, bulkheads, and unfinished basement areas.
Bats can move through these hidden spaces once they have entered the structure from outside.
That is why a bat found in a bedroom or basement did not fly straight in from outdoors. It probably came from the attic, down into the walls beside pipes, wires, chimneys and ducts to an unfinished space inside the home like the basement or furnace room. That’s the most likely way it got in.
Why Bats Show Up in Basements
Basements are the number 1 most common place for bats to appear.
This surprises many homeowners because they assume bats should be in the attic, not the basement. But bats can move downward through wall cavities, chimney chases, plumbing openings, unfinished framing areas, utility spaces, and mechanical rooms.
Finished basements in particular are a favorite place for the common big brown bat to hibernate.
In virtually every case, bats will enter the structure high on the house and eventually emerge in the basement because the basement provides the most openings into the finished living area.
Common basement pathways include:
- Furnace rooms
- Utility rooms
- Open ceiling areas
- Gaps around pipes and wires
- Chimney chases
- Dropped ceilings
- Bulkheads
- Storage rooms
- Unfinished mechanical spaces
Why Bats End Up in Bedrooms, Bathrooms, Kitchens, and Living Rooms
Bedrooms are one of the worst places to encounter a bat, and unfortunately, it happens a lot. Finding a bat in a bedroom is especially concerning when people were sleeping, and if that happens, you should follow public health guidance regarding possible exposure. After that, the home still needs to be inspected to find out how the bat got into the living space.
Unless there is a large hole in the walls of the bedroom, bats can only enter the room in one of two ways: under the door or out of a heat register.
Coming out of a heat register is almost, but not quite, impossible. Bats may dive down heat registers, but getting back out is extremely difficult unless it is a wall register or a ceiling register. Even then, it is still rare and unlikely.
The number one way bats get into bedrooms is under doors. Ontario building code requires air space under interior doors, and bats can take advantage of that space as they crawl and move from room to room looking for a way out.
Bats may also appear in bathrooms, kitchens, hallways, stairwells, basements, and other main living areas for the same reason: the bat is lost. Once a bat comes out of the wall, it may not be able to get back into the same space it came from. At that point, it only has a few days to find its way out before it dies of dehydration.
If you encounter a bat in the middle of the night, it is not there to suck your blood, and it is not trying to attack anyone. It is simply lost and trying to find a way out.
A bat in the living space is often a sign that the house needs more than a quick removal. The structure needs to be inspected.
Why This Happens More Often at Certain Times of Year
Bats can show up inside homes at different times of year for different reasons, but in Ontario, indoor bat calls usually peak in August and September. By then, bat populations are at their highest. Hot weather can also drive bats farther down inside the walls as they try to escape the heat. At the same time, cool basement air can flow up into the walls through gaps in the ceiling around pipes and ducts, further enticing overheated bats to descend.
In late summer and early fall, young bats are flying for the first time. They are inexperienced and more likely to become lost inside a structure. It is also common for curious young bats to explore the same structure they were born in only weeks earlier. Once they become lost inside, their mothers or siblings may come looking for them as well. This helps explain why some homeowners can have several bats inside in a single night.
It is also considered likely that some bats mistake cool basement air for outside air after the sun has gone down. Cool evening air flowing into attics is well known to act as a natural trigger for bats, telling them that evening has arrived and it is time to go out and hunt. In the same way, cool basement air may trigger inexperienced bats living in the walls to believe they can get outside through the basement.
In winter, big brown bats may wake up from hibernation inside walls, attics, basements, or other protected parts of the home. When they wake up, they may move around, look for water, relieve themselves, or try to find a better location. This is when some homeowners suddenly find a bat inside even though it is cold outside.
Bats have to wake up and relieve themselves every few weeks in winter, and they will not usually do that in the walls where they are hibernating. That would be unsanitary, so they often pop into basements and relieve themselves there instead. I know — gross.
The season can help explain what is happening, but the house still needs to be inspected to find the actual pathway.
A Bat Inside Does Not Always Mean There Is a Large Colony
One bat inside does not automatically mean there are hundreds of bats in the attic.
Our most common species, the big brown bat, is highly transient and lives in small colonies that move back and forth among several houses. As we like to tell our clients, when you have big browns, your home is part of an ecosystem of houses being used by the bats.
Bats that live next door will often scout and explore nearby houses to find other potential roosts for themselves and other bats.
Sometimes the bat found inside is one of these scout bats that became lost after entering the structure. Sometimes it is a sign of a larger bat problem.
The important thing to understand is that even one bat means local bats are using the house.
Signs that your colony is larger or growing are
- More than one bat found inside
- Bats droppings in the attic.
- Bats found during winter
- Droppings below roof gaps, vents, chimneys, or siding
- Bats seen flying around the roofline at dusk
- Bat chirping or movement sounds in walls or ceilings
- A history of bats appearing inside the home
If any of these are happening, the problem should be treated as a structural bat issue, not just a one-time indoor bat removal.
Removing the Bat Does Not Fix the Pathway
Catching or removing the bat from the house only solves the immediate problem.
It does not explain how the bat got there.
If bats are moving from the attic, walls, chimney area, basement ceiling, or furnace room into the living space, the home has an internal pathway problem as well as an exterior entry problem.
That means two things need to be understood:
- How bats are getting into the structure from outside.
- How bats are moving from hidden areas into the living space.
Both matter. If only the bat in the house is removed, the same thing will happen again.
Bats that show up inside, can disappear before you can catch them.
Sometimes a bat that appears inside the living space seems to “disappear” before it can be removed. In some cases, it may have found its way back into the wall, ceiling, attic, or hidden space the same way it came out. In other cases, bats disappear down heat registers or duct openings, which is usually a one-way trip.
If a bat vanishes inside the house and you suspect it may have gone into the ductwork, pull the furnace filter to give it a way out. The last thing you want is the smell of a dead bat in your ductwork.
There are only 3 possible outcomes.
A bat only has a few days to live if it becomes stuck inside your living space. When a bat disappears inside a home, there are usually only three possible outcomes: it got back up into the wall, it is hiding and will come out again soon, or you will eventually find it dead — or smell it — in the ducts.
Do Not Seal Random Gaps From the Inside
It may seem logical to start sealing indoor gaps after finding a bat inside the house. However this will not stop bats from living in the building and may not stop them from showing up inside. Interior bat-proofing work should be considered stop gap and a temporary measure until the bats can be excluded and the building bat-proofed.
The correct approach is to inspect the structure, identify the exterior entry points, understand the internal pathways, exclude the bats safely, and then bat-proof the areas that allow them to return.
The only exceptions to this are…
If you live in a townhouse or condo, rent your home, or cannot otherwise afford bat exclusion and bat-proofing work, you should focus on what can be done inside the living space. The goal is to keep bats in the walls and out of your bedrooms until the larger structural problem can be properly addressed.
Unfortunately, homeowners who live in a semi-detached home cannot ever be certain that exterior bat-proofing and bat exclusion will solve the problem completely. Because semi-detached houses are interconnected, bats may enter through your neighbour’s roofline or attic area and still end up inside your home.
In those cases, and for renters and those that cannot afford bat-proofing , I recommend following the instructions in my video, “What Can I Do in the Meantime?”
Why Big Brown Bats Commonly Show Up Inside London Homes
In London, Ontario, many indoor bat calls involve big brown bats.
Big brown bats are well adapted to buildings. They can use attics, wall cavities, soffit areas, chimney chases, and sometimes basement or finished basement areas. They are also the only Ontario species that can be encountered inside homes during colder weather.
This is one reason homeowners may find a bat indoors even when they assume bats should not be active outside.
A winter bat inside the house is often not a random outdoor bat flying in. It is always a bat that was already hibernating somewhere in the structure.
The Real Question Is Not Just “How Did It Get Into the Room?”
When a bat is found inside the home, most people focus on the room where it appeared.
That is understandable.
But the room is usually only the final stop.
The better questions are:
- Where are bats getting into the structure from outside?
- Are they using the attic, walls, chimney area, basement, or furnace room?
- How did the bat move from that hidden area into the living space?
- Are there other pathways that could allow this to happen again?
- What needs to be bat-proofed so the problem stops?
A bat specialist can answer these questions.
Think Bats Are Getting Into Your Living Space?
If you have found a bat in your bedroom, basement, bathroom, or living room, do not assume the problem is solved once the bat is removed.
The bat may have come from a hidden area inside the structure.
Bat Control Specialists inspect the home to determine how bats are entering from outside, where they may be roosting, and how they are getting into the living space. The goal is not just to remove one bat.
The goal is to stop bats from getting inside your home again.
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