A secondary suite is a self-contained dwelling unit — with its own kitchen, bathroom, sleeping area and separate entrance — located within or on the same lot as a principal residence. It is the term that appears in Canadian zoning bylaws and in CMHC’s lending rules, which makes it the word to use when you want the actual regulations rather than the marketing.
- A secondary suite is self-contained: own kitchen, own bathroom, own sleeping area, own entrance
- It’s the canonical planning term — bylaws and CMHC use it; “granny flat” and “in-law suite” don’t appear in regulations
- It cannot normally be sold separately from the principal dwelling
- Ontario, B.C. and Edmonton now permit multiple units as-of-right on most residential lots
- CMHC’s refinance route allows up to 90% of as-improved value to fund building one
Canada has a dozen words for a second home on your property, and only one of them reliably gets you to the rules. “Secondary suite” is what your municipality’s bylaw says, what your building inspector works from, and what CMHC’s lending documents use. Everything else — granny flat, in-law suite, basement apartment, laneway house — is either a regional variant or an informal description.
This guide is the hub for that whole family. It defines the category properly, explains what “self-contained” actually means to an inspector, sets out where suites are permitted, and points you to the specific term your market uses.
What is a secondary suite?
A secondary suite is a self-contained dwelling unit located within a principal residence, or on the same lot as one. Someone can live in it independently and year-round without passing through the main home.
The City of Edmonton’s definition is a useful, precise example: a secondary suite is “a separate dwelling located within a single-detached, semi-detached, backyard house or row house with its own living room, kitchen, bedroom and bathroom,” with “its own separate entrance from the principal dwelling, either from a common indoor landing or directly from outside the building.”
Two structural facts follow from “secondary”:
It is subordinate to the principal dwelling. Not lesser in quality — subordinate in law. The main house is the primary unit and the suite is accessory to it.
It shares the lot and normally the title. Edmonton’s bylaw states it plainly: a secondary suite cannot be separated from the principal dwelling by condominium conversion or subdivision. Most Canadian municipalities take the same position. This shapes financing, insurance, taxation and your eventual exit.
Attached suites — basements, converted floors, additions — are the most common form. Detached versions sit in the rear yard and go by other names depending where you are: laneway house, garden suite, coach house or garage suite.
What makes a suite “self-contained”
This is what an inspector actually checks, and it’s the test that decides whether you have a legal second unit or an expensive bedroom.
Four elements:
- A private entrance — either directly from outside, or from a shared indoor landing that doesn’t require passing through the main dwelling
- A kitchen — a permanent cooking facility, not a hotplate and a bar fridge
- A bathroom — full facilities within the unit
- A sleeping area
Miss any one and it isn’t a self-contained dwelling unit. The kitchen is the one that most often disqualifies a project: people build a comfortable bedroom-and-bathroom suite with a connecting door, and discover it doesn’t meet the definition for zoning, for financing, or for the federal tax credit that requires a self-contained unit.
Beyond the four elements, being legal also requires meeting building code — egress, fire separation, ceiling height, interconnected smoke alarms — which is a separate matter covered in the next section.
Legal, non-conforming and illegal suites
Three categories, frequently confused, with very different consequences.
Legal (permitted and registered). The suite was built under permit, passed inspection, complies with current zoning and code, and — where the municipality maintains a registry — is registered. This is what you want. It’s insurable, financeable, and a buyer will pay for it.
Legal non-conforming. The suite was lawful when built but no longer complies with current rules, and is permitted to continue under grandfathering provisions. Genuinely legal, but with limits: substantial alteration or a period of discontinued use can end the protection, and the rules on this are municipality-specific.
Illegal (unpermitted). Built without permits, or not compliant. Extremely common — informal estimates have long suggested a large share of Canadian basement suites fall here.
The real cost of an unpermitted suite isn’t primarily enforcement risk. It’s this:
- Insurance. An undisclosed rental unit can compromise a claim.
- Financing. Lenders generally won’t count rental income from an unpermitted unit toward qualifying you, which can be the difference in a refinance.
- Resale. A well-advised buyer discounts for it or requires it be removed.
- Incentive programmes. Every suite incentive in Canada pays against legal, registered units.
Legalising an existing suite is its own project, and whether it’s worth it turns on what’s required to bring it to code — sometimes minor, sometimes structural.
Where secondary suites are permitted in Canada
Permission is municipal, set within provincial frameworks that changed substantially since 2022.
British Columbia. The Province of British Columbia’s small-scale multi-unit housing rules require a minimum of three units on parcels of 280 m² or smaller and four on larger parcels, within urban containment boundaries in municipalities over 5,000 people, rising to six near frequent bus service. Secondary suites and accessory dwelling units are permitted province-wide in single-family residential zones.
Ontario. Bill 23 requires most serviced residential lots to permit up to three units as-of-right — three within the primary building, or two plus one in an ancillary structure. The second and third units are exempt from development charges and parkland dedication.
Alberta. No provincial framework; municipalities set their own rules. Edmonton’s Small Scale Residential zone under Zoning Bylaw 20001 permits up to eight units on a sufficiently large mid-block lot. Calgary is in the middle of significant change — see our Calgary guide for the current position.
The word your market uses determines which rules you’ll find:
| Market | Term to search |
|---|---|
| Toronto | Laneway suite (with a lane) / garden suite (without) |
| Mississauga, Brampton | Garden suite |
| GTA satellites | Basement apartment |
| Vancouver, Burnaby, Coquitlam | Laneway house |
| Surrey, Calgary | Secondary suite |
| Edmonton | Garage suite / backyard housing |
| Alberta and B.C. satellites | Basement suite |
What a secondary suite costs and earns
We don’t publish a national cost figure, and you should be wary of pages that do — a basement conversion in an Alberta satellite and a detached build in Metro Vancouver aren’t comparable projects.
What drives the cost: whether the space already exists; ceiling height and whether underpinning is needed; egress requirements, especially below grade; fire and sound separation between units; electrical service capacity for a second kitchen; and provincial cost base — B.C. charges 7% PST on many construction inputs, Alberta has no provincial sales tax.
On what it earns, three honest caveats. A below-grade suite rents for meaningfully less than an equivalent above-grade unit. A detached unit generally outperforms a basement of the same size, because the tenant gets their own building. And any projection that ignores vacancy, maintenance and tax on rental income is a marketing number.
There’s also a tax consideration worth raising early: building a self-contained suite is generally a structural change, which can affect how the principal residence exemption applies to the rented portion of your home when you sell. Worth an accountant’s time before you build.
How CMHC treats a secondary suite
Two things matter for financing.
Rental income can support your qualification. Lenders will typically count a portion of projected rental income from the suite toward your qualifying income — commonly up to half, though the proportion and method vary by lender. This is often what makes a project viable, and it applies only where the suite is legal.
You can refinance against the improved value to build it. CMHC’s refinance product for secondary suites, available since 15 January 2025, allows borrowing up to 90% of the as-improved property value — above the 80% ceiling on a conventional refinance — on properties with up to four units, with as-improved value capped below $2 million. Conditions include owner or close-relative occupancy, funds going to construction rather than equity take-out, no short-term rental of the new unit, and CMHC approval before construction starts.
Properties with one to four units stay in residential mortgage territory. Five or more moves to multi-unit underwriting. Our financing page covers the routes in detail.
Confirm current terms with CMHC or a mortgage professional — products change.
Find out what your property can support
The definition is straightforward. What isn’t is whether your specific property can carry a legal suite — which depends on zoning, the existing structure, ceiling height, egress, and how far servicing has to reach.
HouseLyft’s free property assessment works through those for your address and tells you which forms are realistic. Our your options page covers the paths available to a homeowner from here. When you want a straight answer for your own property, request your free report.
This guide explains zoning, building and financing rules in general terms and is not legal, tax or financial advice. Municipal rules differ and apply lot by lot — confirm your situation with your municipality and a qualified professional before committing to a project.
Checked by Lee Yousaf, Founder