Accessory Apartments

An accessory apartment is a separate dwelling unit, which is located within and subordinate to a single-detached, a semi-detached, or row or townhouse.

On this page:

1. Zoning By-law Amendment No. Z130-2018
2. Other zoning regulations for accessory apartments
3. Benefits of permitting accessory apartments
4. General building permit information
5. Other general information

Zoning By-law Amendment No. Z130-2018

On October 9, 2018, the Town of St. Marys passed Zoning By-law No. Z130-2018 to add regulations to the Town’s Comprehensive Zoning By-law No. Z1-1997 to permit a maximum of one accessory apartment per residential lot, in either of the following situations (but not both) and made further changes in June 2021 by passing Z144-2021:

In a single detached, semi-detached, row or townhouse dwelling

OR

In an accessory building or structure on a lot with an existing single detached, semi-detached, row or townhouse dwelling provided the:

• Accessory building or structure complies with 5.1.3A of the Towns Zoning Bylaw
• Accessory building or structure complies with the building height and lot coverage requirements of the Zoning By-law.

Other zoning regulations for accessory apartments

• The maximum gross floor area of the accessory apartment can not exceed 45% of the gross floor area of the main building or 100 m².
• A home occupation is prohibited in any accessory apartment.
• The lot is serviced by municipal water and sanitary sewer services.
• One additional (non-tandem) parking space is provided for the accessory apartment.
• The lot does not contain a garden suite.
• The lot is not located east of the CNR tracks and north of Trout Creek.

 The Town’s Zoning By-law should be read in its entirety to determine all applicable zoning provisions.

Benefits of permitting accessory apartments

• Provides an additional housing option in the community
• Increases the supply of affordable housing
• Make more efficient use of the existing housing stock
• Creates jobs in the construction/renovation industry
• Provides opportunities for additional income for homeowners
• Allow seniors to live independently while still being close to family or friends
• Can help pay the mortgage and maintenance costs for first time homebuyers

General building permit information

Accessory apartments must comply with the Town’s Zoning By-law, and the Ontario Building Code.  Before you renovate your home to establish, enlarge or alter an accessory apartment, you should contact or visit the Town’s Building and Development Department at the Town of St. Marys Municipal Operations Centre (408 James Street South / 519-284-2340 ext. 242) during office business hours.

Building Permit Information Flyer (PDF)

Other general information

Your property taxes could be impacted by the creation of an accessory apartment.  Please contact the Municipal Property Assessment Corporation for further information.

You should also contact the Upper Thames River Conservation Authority to determine if your property is located within a Regulated Area (1424 Clarke Road, London / 519-451-2800).