My husband and I have been considering our future housing. One concept that keeps arising is building a secondary unit onto our current home.

We know the design of our current bungalow is not very flexible. It was built in the late 50’s for a young family, not an older couple. It’s too much for us but not enough to include more residents. So, we are considering an extension, a secondary unit.

For a number of years we were working in the building trades and have some understanding of how the zoning and permit processes work. We are trying to stay abreast of the current zoning rules that will affect our choices.

Below are a few excerpts plus a link to:

The Second Units Info Sheet from the Ontario Ministry of Municipal Affairs and Housing

Download a printer-friendly version of the info sheet (PDF)


This document is to assist municipalities and the general public to better understand what second units are, why they are important, and the legislative authority behind second units. It provides some examples of specific second unit policy and zoning best practice approaches currently in use in official plans or zoning by-laws by Ontario municipalities.

What are second units?

Second units are self-contained residential units with a private kitchen, bathroom facilities and sleeping areas within dwellings or within structures ancillary to a dwelling (e.g., above laneway garages).

Second units are also referred to as secondary suites, basement apartments, accessory apartments, granny flats, in-law apartments, or nanny suites.

What are the benefits of second units?

Second units increase the supply and range of affordable rental accommodation. In addition, they benefit the wider community in many ways as they:

  • Allow homeowners to earn additional income to help meet the cost of homeownership
  • Support changing demographics by providing more housing options for extended families or elderly parents, or for a live-in caregiver
  • Help create mixed-income communities, which support local businesses and local labour markets
  • Make more efficient use of existing infrastructure, including public transit where it exists or is planned
  • Make more efficient use of the existing housing stock
  • Create jobs in the construction/renovation industry
  • Assist municipalities in meeting their goals regarding affordable housing, intensification and density targets, and climate change mitigation and greenhouse gas emissions reduction.

Where are Second Units Located?

The majority of second units are created through internal alterations, although some are built as additions to the main house or in/above ancillary structures like garages. The size, type (e.g., internal, addition, ancillary structure) and location of the second unit will depend on the size and design of the house as well as its location on and the size of the lot.

Regardless of where they are located second units must comply with health, safety and municipal property standards, including but not limited to, the Ontario Building Code, the Fire Code and municipal property standards by-laws.