A basement apartment in Mississauga is legal when it meets the Ontario Building Code, the Fire Code and the zoning by-law, and is registered with the City. Registration itself is free. What costs money is the building permit and the work needed to pass inspection.
This guide covers what the City requires, the steps, the code items that decide your budget, what units rent for, and how Mississauga’s rules differ from Brampton’s next door.
The short version
| Question | Answer |
|---|---|
| What makes it legal? | A building permit signed off by all City inspectors, then registration |
| Registration fee | None |
| Where can you have one? | In a detached house, semi-detached house or townhouse |
| How do you register? | Email three documents to secondunits@mississauga.ca |
| How do you check a unit? | The City’s Second Units Registry List, updated monthly |
| Typical rent | About $1,800 to $2,600 a month |
What the City calls a second unit
Mississauga defines a second unit as a self-contained living space with its own cooking, sleeping and bathroom facilities, inside a detached house, semi-detached house or townhouse. A basement apartment, an in-law suite and an accessory apartment are all the same thing under this definition.
The City’s rule is direct: every second unit must meet the Building Code, the Fire Code and the zoning by-law, and must be registered.
How to register, step by step
Step 1 of 5: Check the registry
Look up the address on the Second Units Registry List on the City’s website. It is updated monthly. If the address is there, the unit is already legal.
Step 2 of 5: Find out if there is a permit
Registration depends on a building permit for the second unit that every City inspector has signed off. If the unit was built without one, which is common in older homes, you need to apply for a permit now.
Step 3 of 5: Apply for the building permit
You will need drawings of the existing house and the proposed unit, normally prepared by a designer with a BCIN number. The City reviews them against the Building Code and the zoning by-law. The permit carries a fee, and there may be fire inspection fees. The City’s page does not list the amounts, so ask the Building Division at 905-615-4030 or check the current fee schedule.
Step 4 of 5: Do the work and pass the inspections
Inspectors visit at set stages. For a unit that already exists, expect to open some walls or ceilings so the fire separation, wiring and plumbing can be seen.
Step 5 of 5: Register
Email these to secondunits@mississauga.ca:
- Proof that you own the property, such as a tax bill, title or assessment notice.
- A copy of the second unit building permit, signed off by all City inspectors.
- The completed Second Unit Registration Form.
There is no fee for this step. For questions, call 311, or 905-615-4311 from outside the city.
The code requirements that set your budget
These come from the Ontario Building Code and apply in every municipality. They are the items most often missing from an older finished basement.
| Requirement | What it means |
|---|---|
| Ceiling height | At least 1.95 metres, about 6 feet 5 inches, through the living areas. Lower clearance is allowed under beams and ducts |
| Escape window | Every bedroom needs a window that opens from inside without tools, with an opening of at least 0.35 square metres, unless the unit has its own door directly outside |
| Fire separation | The wall and ceiling between the two units must resist fire, generally for 30 minutes, with interconnected smoke alarms |
| Smoke and carbon monoxide alarms | In both units, wired so that one sounding triggers the others |
| Heating and ventilation | Arranged so smoke cannot travel between units through shared ducts, often with a duct smoke detector |
| Electrical | Inspected by the Electrical Safety Authority |
The Building Code does not require the second unit to have its own entrance facing the street. A side or rear door is normal. Your designer will confirm what your house needs, since the rules differ slightly for older and newer homes.
Ceiling height is the item that most often decides whether a basement can be legalized at all. Measure yours first. If it is under 1.95 metres across most of the space, the only fix is lowering the floor, which is expensive.
What it costs
| Item | Cost |
|---|---|
| Registration | Free |
| Building permit and fire inspection | Set by the City’s fee schedule. Confirm the current amount |
| Permit drawings | About $2,000 to $5,000 |
| Upgrading a finished basement to code | About $25,000 to $50,000 |
| Building a unit in an unfinished basement | About $60,000 to $120,000 |
The drawing and construction figures are our estimates, not quotes. They vary with the house and the contractor.
Rent and payback
Second units in Mississauga rent for roughly $1,800 to $2,600 a month, depending on size, location and finish. Units near the Hurontario corridor, Square One, the university campus and the GO stations sit at the top of that range.
Enter your own cost and rent. The calculator starts at a $75,000 build and $1,900 a month. Raise the rent to match your area.
Rent is taxable income, and renting part of your home can affect the principal residence exemption when you sell. Speak to an accountant before relying on the full figure.
Mississauga against Brampton
| Mississauga | Brampton | |
|---|---|---|
| Registration fee | None | $200 |
| Permit fee | Per the City’s fee schedule | $1,186.24 |
| How to register | Email documents after inspections pass | Combined online application for permit and registration |
| Public registry | Registry list, updated monthly | Map of registered units |
| Rental licence | Check current City rules | Required city-wide since January 1, 2026 |
The building requirements are the same in both cities, because they come from the provincial Building Code. The paperwork differs. Our guide to a legal basement apartment in Brampton covers that city’s process.
If the unit is not registered
- The City can act. An unregistered unit can lead to orders to bring it into compliance or stop using it, and to charges under the Building Code Act and Fire Code.
- Insurance. If there is a fire in a unit your insurer did not know about, or one built without a permit, a claim can be reduced or refused.
- Tenants keep their rights. Ontario’s Residential Tenancies Act applies whether the unit is registered or not.
- Selling. Calling a basement “legal” in a listing is a promise the buyer can rely on. Without registration, the accurate wording is “finished basement with separate entrance”. Buyers’ lenders are also more willing to count rent from a registered unit. Our selling guide covers how second units affect a sale.
Buying a Mississauga house for the income
Check the registry list before you offer, and make the offer conditional on confirming registration with the City. Ask for the lease and proof of the rent actually paid. Rent from a registered unit can raise the mortgage you qualify for. Our stress test calculator shows how lenders work that out.
For prices by neighbourhood and home type, see the Mississauga real estate guide.
Questions owners ask
How do I check if a basement apartment in Mississauga is legal?
Look up the address on the City’s Second Units Registry List, which is updated monthly, or call 311.
Is there a fee to register a second unit in Mississauga?
No. Registration is free. The building permit and inspections carry fees.
What is the minimum ceiling height for a basement apartment?
1.95 metres through the living areas, with lower clearance allowed under beams and ducts.
Does a basement apartment need a separate entrance?
It needs a safe way out. The Building Code does not require a separate entrance facing the street, and a side or rear door is usual.
Can I register a basement that was built without a permit?
Yes, by applying for a permit now and bringing the unit up to today’s code.
Sources
- City of Mississauga, “Registering a second unit”: definition, requirement to register, documents, no registration fee, registry list and contacts.
- Ontario Building Code requirements for second units, as summarized in published Mississauga second unit guides.
- Rent range from published 2026 Mississauga second unit guides. Construction and drawing costs are Local Toronto estimates.
This page is general information, not legal, tax or building advice. Confirm current rules and fees with the City of Mississauga. HomeLife Landmark Realty Inc., Brokerage. Not intended to solicit homes already listed for sale.