You need an approved building permit, and you may need a zoning (occupancy) certificate if you plan to have more than one residential unit on your property.

The process on this page applies to residential buildings with two to four total residential units. Visit our residential dwelling units page for information about buildings with five to 10 dwelling units.

On this page:

  1. About dwelling units
  2. Zoning
  3. Types of additional dwelling units
  4. Application process
  5. Resources

About dwelling units

Under zoning bylaw 2019-051, a dwelling unit is a room or suite of habitable rooms that:

  • is in a residential or mixed-use building
  • is occupied or designed to be occupied by a household as a single, independent and separate housekeeping establishment
  • has both a kitchen and bathroom used or designed to be used for the exclusive common use of its occupants
  • has a private entrance directly from the outside of the building or a common hallway or stairway inside the building

The process on this page applies to residential buildings with two to four total residential dwelling units.

Visit these pages for information about:

  • residential buildings with five to 10 total units and no other uses: residential dwelling units
  • buildings or properties with five to 10 residential dwelling units and non-residential uses: site plans


Our zoning bylaw allows for additional dwelling units (ADUs) on residential-zone properties with adequate services if the project meets our zoning bylaw.

To find out which zoning bylaw currently applies to your property and how it is zoned, enter the address into our online zoning map. If you have any questions, call us at 519-741-2426 or send us an email.

Types of additional dwelling units

There are different combinations of additional dwelling units (ADUs) you can build on your residential property in association with a single detached dwelling, a semi-detached dwelling unit or a street townhouse dwelling unit. In all cases, the maximum number of units permitted on a lot is four. You can combine units in different ways, including:

  • one Additional Dwelling Unit (attached): also known as a duplex, secondary suite, basement apartment or in-law suite, build one attached unit to have a total of two units on your property
  • two Additional Dwelling Units (attached): also known as a triplex, build two attached units to have a total of three units on your property
  • Additional Dwelling Unit (detached): you can build a maximum of one detached unit, also called a tiny house or backyard home
  • one attached unit and one detached unit: combine both types of units for a total of three units

Application process

The application process for additional dwelling units has two parts:

If you have any questions, please send us an email or call 519-741-2317.

Zoning confirmation

To confirm that your property is zoned for additional dwelling units, you must request a zoning (occupancy) certificate.

You do not need a zoning (occupancy) certificate for one attached unit (duplex or basement apartment).

In your application, you must include:

  • completed application form
  • property survey
  • zoning plan (fully dimensioned, showing the property lines, existing and proposed buildings, building setbacks and parking spaces)
  • fully dimensioned floor plans indicating all the uses of the spaces
  • elevation drawings
  • existing building drawings

Building permit

Visit our residential building permits page for requirements and application information.


These resources may help with your project: