Legal Basement Apartment in Mississauga: Permits, Registration & Rules (2026)
Short answer: in Mississauga, a basement apartment is legal only when two things are true. One — it was built or legalized under a second-unit building permit and meets the Ontario Building Code, Ontario Fire Code and the City's Zoning By-law. Two — it is registered with the City under the Second Units Registration By-law (0114-2016). The City is explicit: an unregistered unit is not legal, even if it was built with a permit. The upside: registration itself is free.
What Mississauga requires
| Requirement | The rule |
|---|---|
| Where second units are allowed | Detached, semi-detached and townhouse-type dwellings in residential zones |
| Size | Minimum 35 m² of gross floor area; the unit can't exceed 50% of the home's gross floor area |
| Entrance | A separate pedestrian entrance to the unit is required |
| Ceiling height | At least 1.95 m in habitable areas (1.85 m under beams and ductwork) |
| Escape openings | Egress windows or doors sized to code — see our egress window guide |
| Fire & life safety | Fire separation between units, interconnected smoke/CO alarms, Fire Code sign-off |
| Electrical | ESA notification and inspection, separate from the building permit |
How the process works
1. Drawings. Floor plans of the existing and proposed layout with construction details, prepared for a second-unit permit application.
2. Second-unit building permit. A specific class of residential permit that also checks zoning compliance for the unit. Applications go through the City's online portal.
3. Build with inspections. Framing, insulation, plumbing rough-in, fire separation and final — plus ESA for electrical. All inspectors must sign off.
4. Register the unit. Email the completed Second Unit Registration Form, proof of ownership and a copy of the permit to the City (secondunits@mississauga.ca). No fee. Once registered, the unit is on record and legal to occupy.
Do you need a landlord licence too?
As of 2026, no — not for a basement second unit. Mississauga's new rental-licensing pilot applies to apartment buildings of two or more storeys with six or more units, not to houses with a registered second unit. That's a real difference from Brampton, where a separate Residential Rental Licence applies to rented houses in designated wards — we break that down in our rental licensing explainer.
Why bother making it legal
The same three reasons we see play out every year: an illegal unit can be ordered vacated after one complaint or fire inspection; insurance can deny claims involving an unregistered unit; and when you sell, buyers' lawyers ask for the permit and registration paperwork. Legal units also rent to better tenants at better rates — and in Mississauga the City has removed most of the cost barrier to doing it right.
What it costs and how long it takes
With permit fees refunded and free registration, your real costs are design, construction and life-safety upgrades — which depend entirely on what your basement already has: ceiling height, entrance, window sizes, fire separation. A typical legalization or new-build second unit runs two to four months including drawings, permits and construction. We give a fixed written quote after one site visit, and we handle drawings, permits, inspections and registration end to end.
Planning a legal basement apartment in Mississauga? We'll assess your basement in one visit, tell you exactly what the City will require, and quote the full path — drawings, permit, construction, ESA, Fire Code sign-off and registration.
Call (647) 771-0806 or see our basement renovation page. Free, no-obligation estimates across Mississauga, Brampton and the GTA.