Bat-Proofing Older and Stone Homes: What Changes on a Century Home

Yes, an older or stone home can be bat-proofed, and our Lifetime Warranty covers it exactly as it covers a new build. The method does not change: find every gap, let the bats leave through one-way doors, then seal the whole building. What changes is the number of entry points, the materials we use to close them, and the other trades you sometimes need alongside us.

Can a century-old house really be bat-proofed?

Grey Bruce, Simcoe and Huron are full of old houses. Limestone and fieldstone farmhouses outside Owen Sound and Goderich. Brick Victorians on the main streets of Meaford and Collingwood. Board-and-batten cottages along the lakeshores. Rubble foundations, summer kitchens, and additions stacked on additions over a hundred years of family changes.

Owners of these homes are often told, or quietly assume, that a house this old cannot be sealed against bats.

That is not our view. Old houses take more care, more time on a ladder, and sometimes a conversation about a mason or a roofer. Three things change on an older house: there are more entry points to find, the materials have to match the house, and another trade sometimes works alongside us. The sections below walk through each one. What does not change is the method, or the promise behind it.

Why do older houses get bats more often?

Bats are not drawn to old houses because they are old. They are drawn to them because a century of weather and settling creates gaps, and because big open attics make good roosts. A large, unfinished attic is warm, dark, quiet and roomy, which is what a maternity colony wants. Every addition brings new valleys, junctions and dormers, and every old vent, chimney and shake roof is one more candidate opening.

Our guide to how bats get into a house covers the general entry points. Here is how they play out on an older home, feature by feature:

Feature of an older house	Why bats use it	How it gets sealed
Stone or brick meeting wood trim	Settling opens a gap along the junction that leads behind the trim or into the wall	Sealant in the joint, with mesh or flashing where the gap is wide, colour-matched to the trim
Original wood soffit and fascia	Old boards shrink, cup and pull apart, leaving long thin openings along the eaves, right beside the attic	Gaps closed with matching trim, sealant and mesh; one-way doors first at any active entry
Multiple rooflines and dormers	Valleys and junctions create pockets where flashing lifts and trim separates	Each junction sealed individually with flashing and mesh shaped to the roofline
Unscreened gable vents and louvres	Many were never screened, or the screen has rusted apart, so bats fly straight into the attic	Original vent kept in place and screened from behind with fine mesh
Uncapped chimney	An open flue is a direct route into the chimney and sometimes the house	One-way door while bats are present, then a proper cap once the chimney is empty
Failed mortar joints	Open joints lead into the wall cavity, especially near the top of the wall	We seal the gap bats use and refer repointing to a mason; once the repair is done, we seal around it
Cedar shakes or slate edges	Lifted or broken edges create pockets bats can crawl under toward the roof deck	Edges sealed or screened where bats enter; broken roofing referred to a roofer

How do bats get into a stone or brick house?

This is the part that surprises people. Bats do not chew through stone, and they do not need a hole in the masonry. On a stone or brick house they use the places where the masonry meets something else:

• the joint between the wall and a wood window sill or door sill
• the gap above a lintel (the stone or beam over a window or door) where trim has pulled away
• the line where the eaves and fascia sit on top of the wall
• the space behind a downspout or an electrical mast (the pipe that brings the power line to the house) where it was never sealed to the wall
• open mortar joints at the top of the wall, where the roof structure meets the masonry

Sealing on masonry does not mean smearing sealant across the stone face. It means closing the junctions: a bead of sealant in the joint between stone and sill, a strip of mesh tucked behind the fascia, a piece of flashing shaped to the top of the wall.

Here is where we are plain about what we do and do not do. We are not masons, roofers or carpenters. If the mortar is failing across a whole wall, if the chimney crown is crumbling, or if a sill is rotten enough that sealant has nothing to hold on to, that is a mason’s, roofer’s or carpenter’s job. We will tell you when the house needs one. The exclusion still works around that repair: we handle the bat side, the trade handles the repair, and once their work is done we seal around it so the whole building is closed.

Will bat-proofing make a heritage house look patched?

The worry is fair. Nobody wants a bright silver mesh square stuck on a 150-year-old facade. Three things keep the work from looking like a repair:

1. Matching materials and colours. Mesh, flashing and sealant come in finishes that blend with aged wood, dark trim and weathered roofing. We choose what disappears against your house, not what is fastest.
2. Working at junctions, not faces. Almost everything we seal is where two materials meet: under an eave, behind a trim board, at the top of a wall. The stone and brick faces stay untouched.
3. Keeping original vents. An old gable vent or louvre is part of the character of the house. We leave it in place and screen it from behind, inside the attic, so it looks much the same from the street.

If your home is a designated heritage property, exterior alterations may need approval before work starts, so check with your municipality. We are happy to describe exactly what we would do and where, so you have that in hand when you ask.

What about the old chimney?

Older homes often have chimneys that are unlined, uncapped or both, and bats use them. Sometimes the colony is in the flue itself; sometimes they are entering through gaps where the chimney meets the roof. From the ground, you can often see the warning signs: no cap or screen on top of the flue, or open gaps where the chimney passes through the roof.

Our post on getting bats out of a chimney walks through the process. The short version: a one-way door lets the bats leave, and a proper cap is the fix once the chimney is confirmed empty. If the crown or brickwork is failing, that part goes to a mason.

What if the bats are inside the walls?

In stone and double-brick houses, the colony is sometimes living in the wall cavity rather than the attic, a situation we cover in bats in walls vs. attic. The signs are a little different:

• scratching, rustling or chirping inside a wall, most often around dusk and dawn
• small dark droppings collecting at baseboards, on windowsills or on the floor below a specific spot
• a musty or ammonia-like odour near one wall

Old attics bring their own issue. Loose-fill insulation holds guano and odour long after the bats are gone, and a colony that has used the same attic for years can leave a real mess behind. Our attic cleanup service handles that once the exclusion is done.

If you are not sure which situation you have, that is what the free inspection is for. We look at the whole building, inside and out, and talk with you about what you have seen and heard. There is no obligation afterward.

Do empty farmhouses and closed-up cottages get bats?

They can, and they are easy to miss. A stone farmhouse that sits empty for months, or an old cottage closed up for the winter, loses the one thing that usually catches a bat problem early: someone home to hear it. Bats can use a seasonal building for years before anyone notices, and the first clue can be droppings found on a sill, floor or porch when you open the place up.

A few simple checks help:

• When you open up, look for droppings on porches, windowsills and the floor under the eaves.
• Before you close for the season, check gable vents for missing or torn screens.
• Look at the chimney top for a missing cap or screen.

If you own a place like that, read cottage fall bat-proofing before you close up for the season.

Can an older house still be sealed this fall?

The fall exclusion window runs from mid-August, once the pups can fly, to the end of October. If you are reading this in October, the window is closing soon. After that, whether work on an older house can continue depends on one thing: are bats still in the building? Some bats leave for caves and mines, and some stay in buildings over the winter, which we explain in where bats go in winter in Ontario. The inspection is how we find out which is true for your house.

A building confirmed empty of bats can be proofed whenever the weather allows the materials to be installed properly. A building with bats still inside has to wait for the right window, because sealing them in is not humane and not something we will do. Several Ontario bat species are endangered and protected, and harming them is against the law.

Spring brings the other limit. Once maternity season begins, roughly May to early August, flightless pups will soon be in the roost, and exclusion has to pause until they can fly.

Why does the whole house need sealing, not just one gap?

On a newer house there may be a handful of candidate gaps. On a century home there can be dozens. That changes the math on partial fixes. Seal the one opening you found above the porch, and the colony will often move along the eave to the next one. Bats tend to return to the same roost year after year, and they are good at finding the new way in, which is why we wrote do bats come back after exclusion.

Whole-house sealing means every junction, vent, chimney and roofline gets closed in the same job, with one-way doors at the active entries so the bats leave on their own. It is more detail work on an older home, and that is exactly where the Lifetime Warranty earns its keep.

The promise is the same on every building we seal, old or new: if a bat re-enters through any point we sealed, we come back and do the work at no charge, forever. The warranty transfers to the new owners, so it stays with the house if you sell.

What does bat-proofing an older house cost?

We do not quote numbers in a blog post, because every old house is different. What we can say is that an older home usually has more entry points and more detail work at the junctions, and that is what moves the price compared with a simple new build. The inspection comes first, and the quote is based on what we actually find on your house. Our post on what humane bat removal costs in Grey Bruce Simcoe explains what goes into it.

Book a free inspection for your older home

If you own a stone farmhouse, a brick Victorian, an old cottage or any century home across Grey Bruce, Simcoe and Huron, start with a free, no-obligation inspection from our licensed, family-run team. We will look at the whole building, tell you honestly if another trade needs to be involved, and explain how the one-way doors and sealing would work on your house.

You can book through our bat-proofing service page. Every point we seal is covered by the Lifetime Warranty, on a newer house or one built before Confederation.