Bat exclusion

Bats are the one animal on this site where the law, rather than the technique, drives the whole job. Get the timing wrong and you either kill flightless pups or breach protections that carry real consequences. Get it right and exclusion is permanent, because bats do not chew their way back in.

The legal position, stated precisely. Little brown myotis, northern myotis and tri-colored bat are listed as Endangered on Schedule 1 of the federal Species at Risk Act (Canada Gazette listing order). In Ontario they are protected under the Species Conservation Act, 2025 and the Protected Species in Ontario List, O. Reg. 60/26, which came into force on 30 March 2026 and replaced the Endangered Species Act, 2007, now repealed (Environmental Registry of Ontario notice 025-0909). The province states that endangered and threatened bat species cannot be harassed, captured or killed unless landowners enter into an agreement with the ministry (Ontario, prevent conflicts with bats). Exclusion done properly, at the right time of year, is the lawful route.

The timing, which is not negotiable. Ontario's bat exclusion guidance restricts exclusion from mid-May until mid-August, because flightless pups will die if they are separated from their mothers. One-way doors can be installed from April until early May, and again from late August until November once pups can fly. Complete sealing of entrances is appropriate from December until the end of March, once you are sure all bats have left to hibernate elsewhere (Ontario MNR bat exclusion guidance). The province's general advice is to do this work from October to March (Ontario, prevent conflicts with bats). Any contractor willing to exclude your bats in June is proposing something you should refuse.

Step one: inspection and a dusk watch. The inspector looks for staining at gaps, droppings below entry points, and the small gaps bats use, which can be under 15 mm. The most reliable confirmation is a dusk emergence watch, sitting outside at sunset and counting where they come out. This establishes how many entries are active and roughly how many animals are present.

Step two: seal everything except the active exits. All non-active gaps are closed first: ridge and roof-wall junctions, gaps behind fascia, chimney flashing, gable vent edges, and any opening a pencil fits into. This is meticulous work and it is most of the labour.

Step three: one-way devices on the active exits. Netting or tube-style one-way devices are fitted over the remaining exits. Bats leave to feed and cannot return. The devices stay up for a minimum period, generally at least a week of suitable weather, because cold or wet nights keep bats in and a device removed too early traps animals inside.

Step four: final sealing and clean-up. Once the devices confirm no emergence, the last openings are sealed permanently. Guano is removed where accumulation warrants it, with proper respiratory protection, and affected areas cleaned. Roost habitat loss is a real conservation concern, so mounting a bat house on the property is a reasonable and often recommended gesture.

How long it takes. Inspection and a dusk watch are an evening. Sealing is one to three days depending on the building. One-way devices stay up at least a week and often two. Final sealing is a return visit. Realistically this is a two to four week project measured end to end, and it has to sit inside the permitted seasonal window.

What it costs in Ottawa in 2026. Indicative ranges, matching this site's price guide: whole-house bat exclusion generally starts around $500 to $1,500 and goes above it, because the sealing has to be near total. A small, simple, accessible building sits at the lower end. A two-storey house with several rooflines, dormers and a masonry chimney sits well above it, and stone buildings higher again. Guano removal and re-insulation is quoted separately after inspection and often runs $1,500 to $5,000. The drivers are the linear metres of roof edge to be sealed, height and access, whether scaffolding or a lift is required, and how many return visits the device period needs.

What makes an Ottawa house different. Eastern Ontario's bat populations were hit hard by white-nose syndrome, which is why these species are listed at all, and it is part of why the province treats exclusion timing so strictly. Locally, the older housing stock in the core and in villages like Manotick, Richmond and Osgoode offers the gaps bats favour, and the region's many stone and brick buildings have mortar joints and flashing lines that are difficult to seal completely. Ottawa's cold also matters: bats here leave for hibernation sites in autumn, which is what makes the December to March window a genuine opportunity to seal an empty building.

Health, and who to call. Any bat found in living space should be treated as a health matter. Ontario advises that any bat you encounter should be considered rabid unless it is captured and tests negative, to wear gloves and protective clothing when dealing with a bat, and to contact your doctor or veterinarian after direct contact with a person or a pet (Ontario, wildlife rabies). Do not release a bat that has been in a room where someone was sleeping until Ottawa Public Health has advised you, because it may need to be tested.

What to ask before you hire. What is your plan for staying inside the legal exclusion window, and what dates are you proposing. Are you doing a dusk emergence count. How long will the one-way devices stay up. How many metres of roof edge are you sealing and with what. Do you offer a bat house. What is the warranty and how many years. Any contractor unclear about the Species Conservation Act, 2025 and the mid-May to mid-August restriction is the wrong contractor for this job.