Accessory Dwelling Units | City of Belleville

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Accessory dwelling units (ADUs) are separate, self-contained residential units that are secondary to the main dwelling on a property. They may also be known as accessory apartments, garden suites or second units.

The City permits ADUs to increase safe and affordable housing options while providing economic benefits for homeowners. ADUs can also support the housing needs of youth, young families and seniors.

Where ADUs are Permitted

ADUs are generally permitted on properties where a:

one-unit dwelling;
two-unit dwelling; or
three-unit dwelling

already exists, subject to zoning requirements and restrictions.

ADUs may be located:

within a main dwelling (for example, a basement apartment); or
in a detached accessory building on the same property.

The City currently permits up to three accessory dwelling units on a property in the urban area of Belleville, depending on servicing and zoning conditions, and two in the rural area.

Understanding Zoning Requirements

The City’s Zoning By-law Visual Guide illustrates potential locations for accessory dwelling units and summarizes key zoning requirements, including setbacks, building height, maximum floor area, and permitted unit numbers.

View the Zoning By-Law Visual Guide for ADUs

Applicable zoning provisions can be found in Subsection 16.13 of the Zoning By-law.

What Makes an ADU Legal

An accessory dwelling unit becomes a legal, registered unit once all of the following steps are completed:

A building permit has been issued.
All required inspections are completed successfully.
A final inspection and occupancy permit are issued.
Registered units are listed in the City’s Accessory Dwelling Unit Registry, which is updated monthly.

Only units registered with the City are considered legal. If you live in a unit that does not appear on the registry, contact by-law enforcement for verification.

Financial Incentives

The City currently offers an incentive for homebuyers and homeowners constructing new accessory dwelling units through the Community Improvement Plan (CIP). This incentive is called the CIP Program 2: Accessory Dwelling Units Rebate.

The incentive program will provide a $5,000 rebate for each new accessory dwelling unit. Applications are accepted year-round, however, funding is provided on a first-come, first-serve basis and eligibility requirements apply. For more information, please visit the Community Improvement Plan webpage.

Near Permit-Ready Designs

Homeowners may choose to use one of the City’s near permit-ready ADU designs. These plans are intended to simplify the design process and can help applicants prepare drawings that align with typical zoning and Ontario Building Code requirements. While these designs still require site-specific review and may require minor modifications, they can significantly streamline the permit application process.

Near Permit-Ready ADU Designs

You are responsible for ensuring that all approvals required under applicable law in the Ontario Building Code are obtained before submitting your permit application.

Private Services

If your property uses a private sewage disposal system (septic system), the system may need to be evaluated to determine whether it can support the additional load from an accessory dwelling unit. Additionally, a hydrogeological study, prepared to the satisfaction of the City, may be required if the subject land is within an area of known constraint where groundwater quantity or quality may be of concern, or if it is in an area constituting 5 or more existing dwellings/lots occupying 4 hectares of land or less within 300 metres of the new lot boundary.

Applying for a Building Permit

A complete application to construct an accessory dwelling unit must include:

applicable Zoning By-law approval (if required)
completed application package
building permit fees
plot plan
floor or framing plans
cross-section drawings

You must also submit:

Application to Construct or Demolish form

Property owners are exempt from designer qualification requirements, provided the application is not creating a third dwelling unit in total within a singular structure (for example, a single detached with two ADUs). If someone other than the owner submits the application, owner authorization is required.

Apply Online

Required Design Documents

Plot Plan

The City's plot plan application can be downloaded online and submitted with your application. Your plot plan should include:

current use of the building
lot lines and dimensions
distance from buildings to lot lines
lot area, building area and building height
floor area of the accessory unit
driveway and parking locations
landscaped front-yard percentage
location of new entrances (if applicable)
septic system location (if applicable)
overhead electrical conductors (if applicable)
north arrow and municipal address

If proposing a detached accessory unit, reference detached buildings and accessory structures requirements.

Floor and Framing Plans

Provide one floor plan for each level, showing:

fire separations and construction ratings
wall locations and thickness
room uses
window and door sizes and locations
egress windows and doors
plumbing fixtures
smoke and carbon monoxide alarms
exhaust fans and duct sizes

Cross-Section Drawings

Drawings must show:

wall construction details
fire separation details
ceiling and bulkhead heights

Mechanical and Life-Safety Requirements

If a single forced-air heating system serves both units, plans must show:

duct-type smoke detectors
furnace fuel shut-down mechanisms
electrical shut-down mechanisms.

Proprietary Products and Materials

Some construction products sold in Ontario are not automatically approved for use under the Ontario Building Code.

If a product falls outside the Code’s standard requirements, it must have either:

Building Materials Evaluation Commission (BMEC) authorization, or
a Minister’s ruling.

Engineered Design

Part 9 of the Ontario Building Code provides prescriptive structural design rules for houses and small buildings.

If any component falls outside these limits, such as:

roof trusses
point-loaded beams
aluminum or glass railing systems

the design must follow Part 4 structural engineering requirements, typically requiring a professional engineer.

Required Inspections

During construction, inspections are required at the following stages:

framing, plumbing and mechanical rough-in (before insulation)
insulation, air and vapour barriers (before covering)
fire separations and fire-stopping
prior to occupancy.

Any changes from approved plans must be approved by a building inspector before construction. Failure to schedule required inspections may require work to be uncovered for inspection.

Fees

Permit fees are determined by the City’s building by-law.

Typical fees include:

Permit Type	Fee
Building Permit	$7 per square metre (minimum $100)
Plumbing Permit	$15 + $7 per fixture (minimum $50)
Occupancy Permit	$20

Fees do not include any required septic upgrades.