What are Additional Residential Units (ARUs)?
Additional Residential Units (ARUs) are independent residential units, secondary to and in the same building or on the same lot as the main dwelling. They also include separate kitchen, bathroom and sleeping areas. ARUs are permitted on lots containing single detached, semi-detached, and or street townhouse dwellings at a maximum of two per lot.
Important Notice: On August 11, 2026, Council passed By-law No. 45/2026 which introduced amendments to the Additional Residential Unit (ARU) policies under the Zoning By-law. The effect of By-law No. 45/2026 is to more easily permit the development of ARU’s and innovative housing within Port Hope. Pursuant to subsection 34(19.1) of the Planning Act, there is no appeal in respect of the parts of this By-law that permit the use of ARU’s as described in subsection 34(19.1), including ARU specific permissions and standards. Therefore, all the changes related to the new ARU provisions came into effect August 11, 2026. Please contact Planning Services for more information on the recent changes made to the ARU policies under the Zoning By-law during this period of transition.
ARUs are sometimes referred to as granny flats, in-law suites, secondary suites, and basement apartments. Above is a visual sample of ARU examples.
Understanding the Zoning By-Law and ARUs within Port Hope
The following summary from the Zoning By-Law outlines permitted uses and property requirements specific to Additional Residential Units. More information can be found within the Zoning By-Law Document.
| Gross Floor Area (GFA) |
| The zoning by-law defines the gross floor area (GFA) as a total area of buildings measured from the exterior face of outside walls of buildings/structures, excluding areas designed or intended for parking. |
| Parking |
|
Parking is subject to Section 5.6 (Residential Parking Requirements) of The Municipality of Port Hope’s Zoning By-law.
Parking Calculation: Table 5.5 (Residential Parking Requirements)
| Use | Minimum Parking Space Requirement |
|---|
| Additional Residential Unit |
1 space for the first additional residential unit on a lot subject to Section 4.2.1.1 j), with 0 spaces required for the second ARU |
|
| Permitted uses in Residential and Countryside Zones |
Permitted Uses in Residential Zones
| Use | RES1 | RES2 | RES3 | RES4 | RESV1 | RESV2 | RESR | RESE |
|---|
| Two Additional Residential Units (6) |
yes |
yes |
yes |
yes |
yes |
yes |
yes |
yes |
Special Provision 6: Subject to Section 4.2.7
Permitted Uses in Countryside Zones
| Use | A | RU | ORM-C | ORM-EP | ORM-MX | ORM-L | ORM-RU | ORM-RS |
|---|
| One Additional Residential Unit (7) |
yes |
yes |
no |
no |
no |
no |
yes |
yes |
| Two Additional Residential Units |
yes |
yes |
no |
no |
no |
no |
no |
no |
|
| General Provisions with the Urban and Rural Area |
- ARUs must satisfy the provisions outlined in Section 4.10 (Frontage on a Public Street):
- They must be next / have access to a public right of way (ROW)
- A maximum of two bedrooms are permitted inside each ARU
- ARUs in an accessory building must have a 1.2m wide pedestrian path connecting the entrance to the street
- Urban primary dwelling units and ARUs on the same property must be serviced by adequate municipal and water services
- Rural property owners must get confirmation from the County of Northumberland to ensure that existing servicing can support proposed ARUs before a building permit is issued
- ARUs inside accessory dwelling units must be located 40 metres from a public street providing access to the main dwelling unit
- The height of an accessory building cannot exceed 5 metres or the main building, whichever is less
- Required off-street parking spaces may be arranged behind each other
- No additional driveways shall be permitted for ARUs
|
| ARUs Inside a Main House |
- ARUs cannot exceed the building footprint of a main dwelling
- The gross floor area (GFA) of additional residential unit(s), together or separately, cannot exceed 50% GFA of a main dwelling unit
- However, only one ARU is permitted to occupy an entire basement subject to planning approval
- ARUs accessed from the interior side lot must be at least 1.2m from the property line, stairs cannot be inside this setback
|
| Specific Provisions |
| Urban |
Urban Area Detached ARUs:
- They cannot occupy more than 50% of the rear yard area
- A detached ARU must be within 40m of a public street that provides access to the main dwelling unit
- ARUs inside an accessory building must be within 40m from the main building
- The maximum gross floor area of an ARUs cannot exceed 50% of the main building up to a maximum of 70m2
|
| Rural |
- Minimum lot area must be 0.4 hectares.
- ARUs inside an accessory building must be within 40m from the main building
- Only one ARU per lot is allowed inside the Oak Ridges Moraine - Rural (ORM-RU) and Oak Ridges Moraine - Rural Settlement (ORM-RS) zones. It must be in the same building as the primary dwelling unit
- The maximum gross floor area of a detached ARUs cannot exceed 50% of the main building up to a maximum of 80m2 in countryside zones
|
| Restrictions |
- The maximum gross floor area of ARUs within the same building as the primary dwelling unit shall not singularly or together exceed 50% of the GFA of the primary dwelling unit.
- ARUs are prohibited on lands inside an Environmental Protection – Floodplain (EP-F) zone or in a floodplain identified by the Ganaraska Regional Conservation Authority (GRCA)
- Moreover, ARUs are prohibited on lots with a boarding/rooming house, garden suite, bed and breakfast establishment, farm vacation home, garden home type 1 and group home type 2, or accessory farm employee accommodation
- Two ARUs are not permitted in a detached accessory structure
- No more than one ARU is permitted in a basement
- An ARU in a detached accessory structure cannot have a basement or livable spaces below grade
|
|
| Process |
| See the below process to help homeowners plan and build an ARU within Port Hope. |
| Planning Review |
- Submit a planning review form and site plan for staff to verify if ARU proposal meets Port Hope’s zoning standards. This process can take up to 10 business days with a complete application, however, comments from planning staff and outside agencies can delay the process
- Once approval has been given, you can begin the process of applying for a building permit from the Building Services department
|
| Building Permit |
|
Building Permit requirements must be met according to the Ontario Building Code. This varies from project to project based on the scope of the work to be completed.
Review our Building Permits page for details on how to apply.
|
For more information on ARUs, please consult these resources issued by the provincial government:
