Buying a House With a Basement Apartment in Ontario: How to Tell If It's Legal

Allowed and legal are two different questions

Ontario changed the rules in 2022. Under the More Homes Built Faster Act, municipalities have to allow up to three residential units on a residential lot with full municipal water and sewer: the main home plus up to two more units. In Ottawa, that means the main dwelling plus two apartments in the house, or one apartment in the house and one coach house.

That is the zoning side. It tells you a unit is allowed on the lot. It does not tell you the one in front of you was built properly. The City of Ottawa is clear that you need a building permit to add a unit, even when very little construction is involved. A unit someone finished on their own a few years ago can be sitting in a house where it would have been allowed, with no permit behind it at all.

A few things can change the answer before you even get to permits. The three-unit rule is tied to lots on municipal services, so on a well and septic the question is different and the septic capacity matters. And if the house is near water, check whether a below-grade unit is allowed in that area at all. I wrote about what a floodplain designation actually changes separately.

What makes a basement unit legal

For a new or converted unit, the province's guide to adding a second unit lists what the Building Code looks at: ceiling heights, room sizes, windows, plumbing, electrical, fire separation, smoke alarms and carbon monoxide alarms. It calls for a 30-minute fire separation between units. The electrical work needs its own permit and an inspection by the Electrical Safety Authority.

Older two-unit houses are also covered by the Fire Code's retrofit rules for two-unit residential occupancies. In plain terms, those rules look at:

• Fire separation between the two units, generally 30 minutes, or 15 minutes where smoke alarms are interconnected
• Smoke alarms on every level, including the basement, hardwired and interconnected so an alarm in one unit is heard in the other
• A way out: each unit needs a safe way out, and where a window is the second way out, it has to meet size and access standards
• Electrical safety: the fire department can involve the ESA, and hazards have to be corrected by a licensed electrical contractor

That window rule is why I pay attention to basement bedrooms. A small window up near the ceiling can look fine on a showing and still be a problem if it is the only other way out.

How to check before you commit

You do not need to become a building inspector. You need the paper trail, and a few people to read it with you:

• Ask the seller for the building permit for the unit and proof the final inspection was passed. "It was here when we bought it" is an answer, just not a helpful one.
• Check with the municipality. The building department can tell you what permits exist for the address and whether they were closed.
• Ask about ESA and fire inspections. If the unit was ever inspected by the fire department or had an electrical inspection, ask for the records.
• Tell your home inspector it is a two-unit house. A good inspector will look at the separation, alarms and exits, though an inspection is not a permit search. More on that in what a home inspection covers and what it misses.
• Talk to your lender early if you are counting on the rent. Ask how they will treat income from this unit before you rely on it. It is one of the things a mortgage pre-approval does not settle on its own.
• Call your insurer before you firm up and describe the house as it is. Insurers ask about secondary units, and I covered what insurers ask on older homes in more detail.

Permitted unit vs unpermitted unit

If someone already lives there

A tenant in the basement changes the purchase too. In Ontario, an existing tenancy generally continues when the house sells, and ending it has its own rules and timelines under the Residential Tenancies Act. If you plan to move family in or use the space yourself, get your lawyer involved before you write the offer, not after. My piece on Bill 60 and what landlords and tenants need to know covers some of the recent changes.

None of this means a house with a basement apartment is a bad buy. A properly permitted unit can be a real advantage. The point is to know which one you are buying while you still have time to do something about it.