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A second unit — often a basement apartment or an in-law suite — is a self-contained dwelling inside your existing house. In Markham, as across Ontario, these are broadly permitted as-of-right, but whether YOUR lot qualifies depends on its zone, size, servicing and access.
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A second unit (the Province calls it an "additional residential unit", or ARU) is a complete, separate dwelling with its own kitchen, bathroom and entrance, created within an existing house. A basement apartment is the most common form.
It is different from a garden/laneway suite, which is a DETACHED unit in the rear yard — see the garden-suite page for that.
Ontario's More Homes Built Faster Act (Bill 23, 2022) lets most residential lots host up to THREE residential units as-of-right — for example the main house, an internal second unit, and a detached garden suite — without a rezoning, and with no minimum parking required for the added units.
"As-of-right" doesn't mean "no rules". The units still have to meet the Building Code, servicing capacity, and property standards. It means you generally don't need a discretionary planning approval to add them.
The practical gates are: your zone and its regulations, lot size and coverage, adequate water/sewer servicing, a compliant second entrance and ceiling height, and fire separation. Corner lots, conservation-authority regulated land, and heritage designations can add conditions.
SiteIQ reads your parcel against Markham's zoning and flags these in seconds — start with your address below.
Are basement apartments legal in Markham?
Yes — second units such as basement apartments are broadly permitted in Markham, in line with Ontario's province-wide rules, provided the unit meets the Building Code, servicing, entrance and fire-separation requirements for your specific lot.
Do I need a permit for a second unit?
You do not generally need a rezoning, but you do need a building permit and the unit must be registered and meet Building Code and property standards. Always confirm with the City of Markham for your address.
How many units can I have on my lot?
Under Bill 23, most residential lots in Ontario — Markham included — may have up to three residential units as-of-right, subject to servicing and other standards. Your lot's zone and size determine what's feasible.
General guidance, not legal or planning advice. Rules turn on your specific lot and can change — confirm with the City of Markham, and use SiteIQ to read your parcel.