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Second units

A second unit also referred to as a basement apartment, in-law suite or accessory dwelling is a self-contained living space with cooking, sleeping and sanitary facilities within a detached, semi-detached house or townhouse.

All second units must meet the Ontario Building Code, Ontario Fire Code and Zoning By-law requirements and must be registered with the City as stated in the Second Units Registration By-law.

You will need a building permit if you’re planning to construct a new second unit or if your second unit was built after July 14, 1994.

Register an existing second unit

There is no fee to register a second unit. You may need to pay for a building permit, fire inspection fees or any professional design work and renovation costs your second unit may require.

How you register your second unit will depend on when it was built.

To register a second unit built on or before July 14, 1994, email the following documents to secondunits@mississauga.ca:

Once we’ve checked everything is correct and no other approvals are required, we’ll forward the documents to Fire Prevention and Life Safety Staff, who will contact you to arrange an inspection.

You will need to provide inspectors with a current Electrical Safety Certificate.

After Fire inspection

If there is additional work needed, you will be issued a ‘Fire Inspection Order’ outlining the work you need to do to make the second unit safe. A building permit may be required to complete this work.

Once you have addressed all of the outstanding issued identified by the Fire Inspector, they will provide you and the City’s Building Division with a ‘clearance letter’.

When Building Division receives your clearance letter, your second unit will be registered and a copy of the registration certificate will be emailed to you.

To register a second unit built after July 14, 1994, email the following documents to secondunits@mississauga.ca:

  • Proof of ownership such as a tax bill, title of property or tax assessment notice
  • A building permit signed off by all concerned City inspectors. If you don’t have a copy of your permit or need more information please call 311 (905-615-4311 outside City limits).
  • Completed Second Unit Registration Form

Once these documents have been reviewed by staff, the second unit will be registered and a copy of the registration certificate will be emailed to you.

New second units

If you plan to construct a new second unit, you will need to apply for a building permit.

Once a building permit has been issued and all necessary inspections completed, the second unit will be registered.

A copy of the second unit registration certificate will be emailed to you.

Second Units Registry List

Once a second unit is registered, it will be added to the Second Units Registry List, which is maintained by the City and updated the first week of every month.

Report an illegal second unit

To report an illegal second unit, first check the Second Units Registry List. If it’s not registered, then call 311 (905-615-4311 from outside City limits).