Additional residential unit (ARU) permits in London: forms, plans and fee

Check whether you need a permit

An Additional Residential Unit (ARU) is a self-contained dwelling unit located within the same building, or on the same lot, as an existing residential unit. Self-contained means that it has its own kitchen and washroom facilities, and a separate entrance.

A building permit and a residential rental unit license are required for all ARUs.
An approved building permit is required prior to any construction.

1. Determine ARU type

Each ARU type has different requirements, and the information needed for a building permit is different.

interior/basement conversion
converted garage
detached
addition to existing building

2. Zoning compliance

Zoning review is completed by the City as part of the building permit process, but zoning regulations may impact the type of ARU you can create on your property.
ARUs are permitted when the zoning allows for single detached, semi-detached, duplex, triplex, converted or street townhouse dwellings, to a maximum of four (4) total dwelling units.
Under the Council-approved Interim Control By-law CP-1600-300, an Additional Residential Unit (ARU) cannot exceed 80% of the gross floor area of the primary dwelling.
ARUs are permitted on the same lot as a single detached, semi-detached, duplex, triplex, converted or street townhouse dwellings.
A maximum of three (3) ARUs are permitted per lot. Two (2) of the additional residential units can be in a detached building.
No additional parking is required for ARUs. Additional driveways to serve an ARU are not permitted.
Detached ARUs can only be in the rear or interior side yard. (It cannot be in the front yard or between the main dwelling and the street on a corner lot)
Detached ARUs must comply with the lot’s overall landscape open space and lot coverage requirements. The total combined footprint of all buildings on the property cannot exceed a percentage of lot area, and the lot must maintain a minimum percentage of landscaped open space that is not occupied by buildings or parking areas.
These bedroom limits are temporary regulations established under Council-approved Interim Control By-law CP-1600-300. Each ARU is limited to a maximum of two (2) bedrooms.
ARUs within or attached to the main building: A combined maximum of three (3) bedrooms is permitted across all ARUs located within or attached to the primary dwelling.
ARUs in accessory buildings (e.g., detached ARUs): A combined maximum of three (3) bedrooms is permitted across all ARUs located in an accessory building on the property.
Use CityMap to locate your property and the zone code.
If you are proposing a detached ARU, it must follow the Accessory Building regulations outlined in Section 4 of the Zoning By-law, including Section 4.1 – Accessory Uses and Section 4.37 – Additional Residential Units.
Please note: Certain zoning regulations related to ARUs are temporarily superseded by the Council-approved Interim Control By-law CP-1600-300, which introduces additional restrictions that apply while the by-law is in effect.
To confirm permitted uses and zoning regulations visit our zoning webpages, call 519-930-3510 or email zoning@london.ca
If your property or project does not meet the requirements of the zoning by-law you may apply for a minor variance or a zoning by-law amendment to change the regulations if you cannot change your project plans.

3. Building permit process

The property owner may submit their own plans or hire an architect or a qualified designer with a Building Code Identification Number (BCIN) to draft and sign the architectural floor plans for the proposed ARU.
A qualified heating, ventilation, and air conditioning (HVAC) designer with a BCIN must design the proposed HVAC layout and where pre-engineered roof trusses are proposed, the roof design must be stamped by a Professional Engineer.
There are different Ontario Building Code requirements depending on the project. Different properties and building types will have different submission requirements and fees.
If you need assistance with your building permit application, please email building@london.ca or call 519-661-4555.

4. Servicing

Water and sewer servicing must be able to accommodate the increased residential development you want to build.
To confirm servicing call 519-930-3500 or email PlanDev@london.ca
Note: Internet, phone, gas, and electricity are not services delivered by the City of London. Please contact you local utility provider.

5. Building and Fire Code

All construction must meet the requirements of the Ontario Building Code and Ontario Fire Code.

Only if you are proposing a detached ARU

6. Lot grading, for a detached ARU

Detached ARUs must be designed to ensure existing drainage patterns on the property and surrounding area are maintained.

Key requirements

Key requirements include:

Must take existing lot grading and drainage patterns into consideration during design.
Must not locate ARU within a swale or overland flow route.
Proper lot grading must be maintained to ensure drainage functions effectively on both the subject property and adjacent properties.
As part of the ARU approval process, you may be required to submit a lot grading plan for review.
Water from downspouts must not be forced onto neighbouring properties.

Only if you choose a design from the CMHC Housing Design Catalogue

Using a CMHC catalogue design

The City of London now supports use of all the Ontario region designs from the Canada Mortgage and Housing Corporation (CMHC) Housing Design Catalogue. The Additional Residential Units (ARU) types will work in many different zones in London, but please note that not all housing types are permitted on every lot. Zoning regulations such as setbacks, minimum lot width, maximum lot coverage, parking, and driveway widths will apply.

How It Works

Choose a design from the CMHC Housing Design Catalogue
Work with a qualified professional to prepare your lot-specific drawings. Catalogue designs are “near permit-ready” and must be adapted to your specific lot.
Submit a complete building permit application
Receive review within 10 business days

You will need a qualified professional to

You will need a qualified professional (e.g., licensed designer with BCIN, architect, or engineer where required) to:

Prepare a site plan and confirm zoning compliance
Design foundations and grading
Complete servicing details and energy selections
Finalize material and finish selections

Complete the forms3

Submit your application

Follow these simple steps to apply online through our Development & Business Portal.

1. Create an account: Set up an account to access our online Development and Business Portal. This will allow you to manage your application and track its progress.
2. Submit your application: Log in to the Development and Business Portal and click the “Add New Permit” button to begin your application. Follow the steps to enter the required information, download the necessary documents, and pay the applicable fee.
3. Pre-screen review: After submitting your application and paying the fees, the City will start a pre-screen review to ensure the required documentation has been submitted to ensure the building permit application is a complete application and deemed on-the-clock.

Pay the fee

Permit fee paid upon permit submission
A building permit will be required for any new ARU. The cost of a building permit is determined by the size of the project, the amount of work done, and the type of building being constructed or renovated.
Different properties and building types will have different submission requirements and fees.
To encourage the supply of smaller housing units, the Province of Ontario has exempted certain ARUs from development charges, subject to specific conditions.
To determine whether development charges apply to your ARU project, email building@london.ca or call 519-661-4555.
There is a licensing program for all rental units. The program's intent is to protect the health and safety of persons residing in residential rental premises. Licensing of ARUs will include inspections.
Several ARU programs are available with forgivable loans of up to $45,000 for homeowners constructing a new ARU subject to eligibility requirements.