Secondary Dwelling Units: A homeowner’s legal guide for taking advantage of this great opportunity!

With more people moving into popular urban areas, there is a shortage of affordable housing within the City. Millennials, among others, have been forced to find solutions to cover the high cost of housing, sometimes living with parents well into their adult years. For others, utilizing extra space in their homes to generate additional income to offset the costs of home ownership is critical. As a homeowner, your housing needs may also change over time. Secondary dwelling units can provide housing options for family, friends, caregivers or even a tenant while still affording privacy and independence. Consistent, additional income may keep extended families together or allow the elderly to age at home and maintain ties in the community. Secondary dwelling units are flexible and allow homeowners to adapt to environmental, lifestyle and financial changes.

What are secondary dwelling units?

A secondary dwelling unit is a single, self-contained rental apartment within an existing home. A secondary unit has its own private bathroom, kitchen, living and sleeping areas. Most know these spaces as basement apartments, granny flats or in-law suites.

What does the City think about adding a secondary dwelling unit to your home?

In the City of Ottawa, secondary units have been permitted within detached, linked-detached and semi-detached dwellings since 2005. By 2014, regulations expanded to allow second units within townhouses and duplexes. With the exception of Rockcliffe Park, homeowners are permitted to convert or construct this separate living space after obtaining a building permit and meeting additional requirements under the Fire Code and Ontario Building Code. In addition, there are various other requirements and restrictions regarding the construction and maintenance of secondary dwellings.

Renting out your home: Complying with zoning by-law regulations

The requirements for secondary dwelling units are outlined in Section 133 of the City’s Zoning By-law Regulations.

The secondary unit must be located on the same lot and within the same building as the primary or main dwelling unit. The primary dwelling must not be capable of being severed and neither a garden suite, coach house, being new freestanding structures, nor any rooming units are permitted on the lot. A second unit is not permitted where a principle unit contains more than six bedrooms and a secondary unit has more than 2 bedrooms. In addition, the number of bedrooms combined cannot exceed a total of 8.

A maximum of one unit can be installed on any floor of the house, except for duplexes which only allow a secondary unit in the basement. The unit must not be greater in size than 40% of the total floor area of the main dwelling unit. Where the secondary unit is only in the basement, it may occupy the entire area of the basement and there is no maximum size. If an attached garage is converted to create the unit, this space is included in calculating the total floor area.

Entrances to the new unit must be on the ground floor unless building and fire codes dictate otherwise. No new doorway entrance can be added to the front wall but an internal shared lobby or foyer with a common doorway entrance in the front wall is permitted. There are exceptions for entrances on corner lots.

Both units must share the parking area and the yards. No new or additional parking area is required for a secondary dwelling unit, but where provided, must be in conformity with the parking provisions of the by-law, including the requirement that parking must not be located in the front yard. The creation of a parking space must not eliminate a required parking space for the principal dwelling unit. In the case of corner lots, a new driveway may only be created in the yard that did not contain a driveway prior to the conversion.

Additional factors to consider

Building a unit involves obtaining a building permit. You must prepare building plans for this unit, which must be submitted and reviewed by the City before the issuance of your permit, to ensure compliance with Fire Code and Building Code, in addition to by-law requirements.

After the addition is completed, you may need to adjust your insurance policy to reflect changes in liability and the increase in value of your home.

In addition, familiarize yourself with Ontario’s Landlord and Tenant laws as they may apply to your living situation. Consult with a lawyer to determine whether the Residential Tenancies Act will apply to your unique circumstances.

Lastly, you may wish to consult with your accountants and financial advisors who will be able to properly advise as to any reporting requirements for additional income or write offs which may be available.


Secondary dwellings are an exciting opportunity. RSR’s lawyers can assist in navigating the creation of a unit, or in the purchase or sale of a property in which one is found.