Additional Residential Units

What is an Additional Residential Unit (ARU)?

An ARU is a self-contained residential unit with a private kitchen, bathroom facilities and sleeping areas within dwellings or within structures ancillary to a dwelling. Additional Residential Units are also referred to as second units, basement apartments, accessory apartments, granny flats, in-law apartments or nanny suites.

Why Additional Residential Units?

The City of Peterborough is permitting the creation of ARUs to achieve the following objectives:

• To provide housing for a variety of users including aging family members, adult children, caregivers etc.
• To increase the supply of rental housing and improve rental affordability
• To alleviate the cost of homeownership
• To make efficient use of infrastructure, housing stock, land and resources
• To facilitate residential intensification, mitigate climate change, and reduce greenhouse gas emissions

Obtaining a building permit

The information below is intended to familiarize homeowners and their contactors with general requirements set out by the Ontario Building Code, and applicable law to help assist in obtaining a building permit for construction of new or conformity of existing Additional Residential Units.

Sections below outline general submission requirements such as types of documents and drawings necessary for review of an Additional Residential Unit construction, as well as comprehensive requirements applicable to the construction of living spaces and safety requirements such as fire prevention.

Permit applications for Additional Residential Units are to be submitted through the online application portal.

Submission Requirements

1. Completed Building Permit Application Form – generated in the portal to be signed.

2. Drawings/plans drawn to scale and fully dimensioned either in metric or imperial but not in combination. Drawings must include:
   • Site Plan
   • Existing Floor Layouts
   • Proposed Floor Layouts
   • Cross Sections and Wall/Ceiling/Fire Separation Construction Details
   • Elevations showing ARU Entrance and Egress Window
   • HVAC and mechanical drawings

The site plan and lot grading and drainage plan must clearly indicate an unobstructed and maintained path for firefighting access that meets the requirements of Section 6.33.3(d) of the City’s Zoning By-law. This must be provided to and approved by Engineering Development before permit may be granted. 

If constructing an ARU in an ancillary/accessory building, proof that the existing sanitary and domestic cold water (DCW) services will adequately support the increased load. An engineer possessing PEO designation will be required to verify/design the plumbing systems to ensure they meet the OBC. Only one sanitary and DCW service from the City services is permitted per property.

Drawings are to be prepared by a professional such as an engineer, architect, or a designer with a Building Code Identification Number (BCIN). See notes 1 and 2 below.

1. If there is a Principal Unit with one additional residential unit within the dwelling, the homeowner may be permitted to prepare the drawings. It is recommended that the owner engage the services a BCIN designer qualified with a minimum House

2. If there are a total of three (3) dwelling units within the dwelling, a designer with minimum qualifications in Small Buildings is required.

General Design Requirements

• Carbon Monoxide alarms are required adjacent to each sleeping area
• Each unit shall have access to common laundry facilities or have connections within each unit for the connection of laundry appliances
• Minimum required dwelling unit size is 30 m2 and meet minimum room sizes as per Ontario Building Code requirements

Note: This design advice does not cover all requirements for ARUs.  It is the designer’s responsibility to ensure compliance with the current Ontario Building Code.  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.