Adding an apartment (Secondary Dwelling Units)

Adding a single, self-contained rental apartment to your home provides your family with an additional source of income and provides your community (or a member of your family) with another source of affordable housing. These apartments – technically called secondary dwelling units  – are regulated by the Zoning By-law.

Important things to consider before adding a unit to your home

  • If you are adding and/or building a unit in an existing dwelling, you need a building permit before proceeding. The construction may include alterations of existing walls, enlarging any window, adding a new exterior door or an internal shared entrance, or even include an addition however, even if there is limited or no work proposed, the proposed “Change of Use” must be reviewed to ensure compliance with the provisions of the Ontario Building Code and other applicable law.
  • No more than an amount equal to 40 per cent of the gross floor area of the principal dwelling may be developed for a secondary dwelling unit, except where a basement unit is created, in which case, there is no maximum size.
  • The new unit must have a separate access on the ground floor of a principal dwelling (unless building or fire codes allow something else). The creation of a secondary dwelling unit must not result in any new doorway entrance added to the front wall (the closest wall to the front lot line).  An internal shared lobby or entrance hall with a common entrance in the exterior wall facing the front yard is permitted.
  • The new unit must be on the same lot as the principal dwelling unit and must not change the streetscape character along the road on which it is located.
  • No additional parking space is required but where a new one is provided, it cannot be located in the front yard. Tandem parking in the existing driveway is permitted.

Development Information Officers

A Development Information Officer (DIO) can advise on zoning regulations impacting your accessory building design such as setbacks to lot lines, building height and lot coverage. If you require the services of a Development Information Officer, please call 613-580-2424, ext. 23434 or

Adding a Second Unit in an Existing House – Ontario Building Code Information


  • Prior to 2005, secondary dwelling units were permitted in the following former municipalities. All units that existed before 2005 in these areas must comply with the Ontario Building Code and Fire Code:
    • Cumberland-Urban
    • Gloucester
    • Nepean-Urban
    • Osgoode
    • Goulbourn
    • West Carleton

Financial considerations

  • Your property taxes, as determined by the Municipal Property Assessment Corporation, may change as a result of adding a secondary dwelling unit in your home.
  • Rent counts as additional income under the Income Tax Act, so adding a secondary dwelling unit will affect your income taxes.
  • Notify your insurance company or broker as early as possible about your plan to build a secondary dwelling unit. Your policy may need to be adjusted to reflect the changes in liability and the adjusted value of your home after the addition is completed.
  • Financial assistance is available through the Canada Mortgage and Housing Corporation’s Homeowner Residential Rehabilitation Assistance Program for certain secondary dwelling units.

Approximate cost: Refer to Applicable Fees

Approximate timeline

Approximate timeline based on City Council approved enhanced service level:• First review - 15 business days

At key stages of building construction, your work must be inspected to ensure that the applicable stage of completed construction complies with the Ontario Building Code. The permit plans and specifications must be on site and made available to the Building Inspector at the time of inspection. To ensure the availability of a Building Inspector, you should book inspections 48 hours in advance. The Building Inspector's name and phone number are identified on the building permit. Failure to have the appropriate inspection performed may result in your having to uncover and expose the work for inspection, or other Orders issued etc.

Building Code Service counters are open for personal services by appointment only. This includes the submission of permit applications, payment of fees and the issuance of permits. 

There are various methods for submitting applications.

Application Forms: Application for a Permit to Construct or Demolish