Additional Residential Units Guide: Building a New ARU

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SERVICE ANNOUNCEMENT: Bill 23 and Additional Residential Units
New Regulations for Additional Residential Units

Please note that the City’s requirements for Additional Residential Units (previously known as Secondary Suites) have changed effective August 28, 2023 pursuant to By-law 23-087

Bill 23, More Homes Built Faster Act, 2022 was introduced by the Province on October 25, 2022. Third reading and Royal Assent was granted on November 28, 2022. The new legislation makes amendments to nine different statutes, including the Conservation Authorities Act, the Municipal Act, 2001, the Ontario Heritage Act, the Ontario Land Tribunal Act, 2021, and the Planning Act. The associated regulations relating to additional residential units came into force on December 23, 2022.

With the intention of increasing the supply of housing, the Province introduced changes to the Planning Act to allow gentle density/intensification by requiring municipal zoning to permit ‘gentle intensification’ of up to 3 units per lot (up to two in the main building and one in an accessory building or up to three in the main building) in a detached, semi-detached or townhouse dwelling; prohibiting municipal zoning to regulate minimum unit size or from requiring more than one parking space per unit for ‘gentle intensification’ units; and exempting ‘gentle intensification’ units from Development Charges, Parkland and Community Benefit contributions.

Where are Additional Residential Units (ARUs) permitted and what are the size restrictions?

  • Subject to compliance with Zoning By-law 1997-123, ARUs are permitted:
    • Configuration 1:
      • (1) One ARU within a permitted single detached dwelling, semi-detached dwelling or a row dwelling; and
      • up to (1) One ARU within a building that is accessory to one of these permitted dwellings
    • OR Configuration 2:
      • (2) Two ARUs within a permitted single detached dwelling, semi-detached dwelling or a row dwelling
    • The principal dwelling must be a permitted land use in the City’s Comprehensive Zoning By-law 97-123; and
    • Maximum floor area for an Additional Residential Unit must be less than the Floor Area of the Principal Dwelling Unit; and
    • Maximum of 2 bedrooms in an Additional Residential Unit: and
    • The ARU must be serviced by public water distribution and wastewater collection facilities unless municipal water distribution and wastewater collection services are not otherwise required by the Zoning By-law for the Principal Dwelling Unit, then the use of private services to support the Additional Residential Unit(s) will be permitted: and
    • The ARU must not be located in a floodway as defined in the Provincial Policy Statement, 2020 or any successor thereof

Zoning By-law Regulations: Detached ARUs

Zoning Regulations for ARUs located in detached accessory buildings
Number of Principal Dwelling Units on Lot Minimum Distance to rear of Principal Dwelling Minimum Distance from the Side or Rear Lot Line Maximum Height Maximum combined Lot coverage for all accessory buildingsa
1 or 2 1.2 metres
(3.9 feet)
0.6 metres
(2 feet)
4.3 metres (14.1 feet) 10%

aCumulative lot coverage of all accessory buildings (e.g. ARU, sheds, detached garages, etc.) plus coverage of the Principal Dwelling must comply with the overall lot coverage regulation of the applicable Residential Zoning District.

Zoning Regulations for Secondary Suite Graphic

Access Route

  • Exterior access to Additional Residential Units shall:
    • be clear and unobstructed (including utilities protruding from the building);
    • be constructed of a hard and stable surface;
    • minimum width of no less than 0.9m;
    • cross-fall: 2% min - 5% max;
    • longitudinal slope 2% min – 8% max;
    • wherever feasible, stairs shall be avoided;
    • drainage function of swales, typically located on properly lines, shall be maintained;
    • external pass-through sheet drainage across access walkways are not permitted;
    • where minimum access requirements are shared across properly lines between multiple properties, registered easements on title shall be required.
  • An access route from a fire hydrant to a pumper vehicle plus an unobstructed path of travel for a firefighter from the vehicle to the primary entrance of a ARU must not exceed 90 metres (295 feet), and,
  • An unobstructed path of travel for a firefighter from a pumper vehicle to the primary entrance of a ARU must not exceed 45 metres (147.6 feet).
  • Where these distances can not be achieved, an alternative firefighting or access solution is required that promotes public safety to the satisfaction of the Peterborough Fire Services and the City of Peterborough Building Services Division.

Parking Requirements

Parking inside a garage can count toward fulfilling the required parking provided the garage interior meets the minimum parking space size requirement outlined below. Parking spaces are not permitted in the road right of way. A survey may be required to confirm the location of the proposed spaces meets the minimum requirements. Parking must be located on the property in accordance with the by-law requirements outlined below:

Parking Requirements by Dwelling Type and Area in the City of Peterborough
Principal Dwelling Type Parking Area 1 Parking Area 2 Parking Area 3
Single Detached 1 space for principal dwelling, 0 spaces for ARU 1 space for principal dwelling, 1 space for ARU 2 spaces for principal dwelling, 1 space for ARU
Semi-detached 1 space for principal dwelling, 0 spaces per ARU 1 space for principal dwelling, 1 space for ARU 2 spaces for principal dwelling, 1 space for ARU
Row or Townhouse 1 space for principal dwelling, 0 spaces per ARU 1.5 spaces per principal dwelling, 1 spaces per ARU 1.75 spaces per principal dwelling, 1 space per ARU

Table Note. Tandem parking for an ARU is permitted in all parking areas. Where the required number of parking spaces results in a fraction, the parking requirement is rounded up to the nearest whole number. 

Parking Areas

To identify which Parking Area applies to your property, please use our interactive map tool:

  1. Enter the address of the property in the search bar
  2. Click anywhere in the highlighted property box (the map will identify the Parking Area for the property) 

Additional Parking and Driveway Regulations

  • Minimum size of a parking space:
    • Parking Area 1: 2.5 metres (8.2 feet) by 5.5 metres (18 feet)
    • Parking Areas 2 and 3: 2.7 metres (8.9 feet) by 5.7 metres (18.7 feet)
  • On any lot containing a single-detached dwelling or a semi-detached dwelling as the Principal Dwelling, no more than two motor vehicles can be parked within 6 metres of a streetline (i.e. a mutual property line with a street).”
  • Where a parking lot contains five or more parking spaces, the parking lot and the driveway must maintain a minimum 1.5 metre (4.9 feet) setback from a side or rear lot line
  • Maximum driveway width at the mutual property line with a street:
    • Single detached or row/townhouse lot with less than 9 metres (29.5 feet) of lot width: 3 metres
    • Single detached or row/townhouse lot with 9 metres (29.5 feet) or more of lot width: 6 metres (19.6 feet)
    • Semi-detached residential lot: 3 metres (9.8 feet) per driveway

Note: Permitted driveway widths may vary where site specific permission has been granted.  Please confirm driveway width requirements with City staff.

Additional Parking Regulations - Lot Widths

  • Maximum number of driveways:
    • Lots containing a single dwelling or a semi-detached dwelling that have a lot width of less than 20 meters (65.6 feet): 1 per Principal Dwelling
    • Lots containing a single dwelling or a semi-detached dwelling that have a lot width of 20 metres (65.6 feet) or more: 2
    • Lots containing multiple Principal Dwellings, such as a block of row/townhouse dwellings, with private entrances at grade: 1 per Principal Dwelling
    • Other lots (e.g. corner lots): 1 per streetline

Maximum Number of Driveways per Lot Widths


I would like to install an apartment in my house with more than two bedrooms

Apartments in houses with more than two bedrooms are not considered ARUs and therefore require zoning that specifically allows for more than one dwelling unit on a property (e.g. Residential District 2 - R.2)

What if my property cannot meet the minimum parking requirements?

If additional parking cannot be provided on the property, the construction of an ARU may not be possible under current conditions and the property may need to be re-zoned. Please contact the City’s Planning Division for additional information on your property

I would like to apply for a building permit for my ARU

Please visit “Building Permit Application Requirements for ARUs Guide” or visit Building Services Division in City Hall located at 500 George Street North (Carnegie Wing of the building. Red Brick Building. Entrance on George Street).

Disclaimer: The design examples, including sample drawings, in this guide are not advice nor do they address all the requirements for legally establishing an ARU . It is each property owner’s responsibility to ensure compliance with all current applicable law, including the Ontario Building Code, the City’s Comprehensive Zoning By-law and any other provisions or regulations applicable to ARUs. A copy of the Ontario Building Code (Ontario Regulation 332/12 made under the Building Code Act, 1992) is available online through the e-Laws website.