Exterior of a garage window

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.

ARUs are sometimes referred to as granny flats, in-law suites, secondary suites, and basement apartments. Below is a visual sample of ARU examples.

Diagram 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

For ARUs within the main dwelling refer to the Accessory Apartment Guide and Requirements
For detached ARUs refer to the Accessory Building Guide and Requirements

For more information on ARUs, please consult these resources issued by the provincial government:

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Additional Residential Units

What are Additional Residential Units (ARUs)?

Understanding the Zoning By-Law and ARUs within Port Hope