As-of-Right Secondary Suites Ontario refers to the provincial rules that allow up to three residential units on most lots without requiring a zoning by-law amendment.
This article explains how Bill 23, municipal bylaws, and the Ontario Building Code work together to determine what you can legally build and when a building permit is still required.
In Ontario, most residential lots are now permitted to have up to three residential units “as of right,” meaning no zoning by-law amendment is required.
However, a building permit and full compliance with the Ontario Building Code are still mandatory.
This framework stems from provincial changes under Bill 23 (More Homes Built Faster Act) and amendments to the Planning Act, but municipalities control implementation details.
Understanding the difference between zoning permission and construction approval is essential before adding a secondary suite, Additional Residential Unit (ARU), garden suite, or fourplex conversion.
Homeowners planning structural changes often consult experienced cottage builders in Ontario to ensure zoning eligibility aligns with construction feasibility and Ontario Building Code requirements.
“As-of-right” zoning means a use is permitted without requiring a rezoning or minor variance, provided it complies with existing municipal zoning by-laws.
In Ontario, provincial legislation requires municipalities to allow additional residential units in most serviced residential areas.
Under amendments linked to Bill 23 and the Planning Act (Ontario), homeowners can generally establish:
Up to three residential units per lot
In the primary dwelling and/or an accessory structure (such as a garden suite)
However, as-of-right does not eliminate the need for:
Building Permit approval
Compliance with the Ontario Building Code (OBC)
Fire separation and egress requirements
Local servicing standards (water, sewage, setbacks)
The Province sets the legal floor.
Municipal zoning by-laws define the practical ceiling, and homeowners should review the official Ontario government guide to understand how provincial ARU permissions translate into local building permit requirements.
Ontario now requires municipalities to permit Additional Residential Units (ARUs) as-of-right in:
Detached houses
Semi-detached houses
Townhouses
This typically allows:
Two units in the main dwelling, plus
One unit in an accessory structure (e.g., garden suite)
Under Ontario’s as-of-right secondary suites rules, most residential lots may contain up to three units: two in the main dwelling and one garden suite (ARU).
The intent of the More Homes Built Faster Act is to increase housing supply without requiring rezoning applications. Municipalities must update their zoning by-laws to reflect this mandate.
| Rule | What It Means |
|---|---|
| 3 Units Maximum | Total units per lot in most residential zones |
| No Rezoning Required | If criteria are met |
| Development Charges | Often reduced or exempt for ARUs |
| Municipal Variation | Design and servicing rules differ by city |
Some municipalities, such as Toronto, have expanded permissions further to allow fourplexes as-of-right citywide. Others may impose stricter design or servicing constraints.
Even if zoning permits the unit, construction must comply with the Ontario Building Code (OBC) regulation.
According to Ontario.ca guidance, homeowners must apply for a building permit through their local building department before beginning work.
Even when secondary suites are permitted as-of-right in Ontario, homeowners must follow a four-step building permit process and comply with the Ontario Building Code.
Fire separation between units
Proper egress windows or exits
Minimum ceiling height requirements
Independent or properly designed HVAC systems
Smoke and carbon monoxide alarms
Plumbing and electrical compliance
Failure to meet OBC standards can result in stop-work orders or fines.
“As-of-right” refers only to zoning permission — it does not waive safety regulations.
While provincial legislation sets baseline rights, municipalities interpret and apply zoning differently.
Municipal comparison of as-of-right secondary suites Ontario rules, showing how unit limits and garden suite permissions vary between Toronto, Stratford, Hamilton, and other cities.
| Municipality | Units As-of-Right | Garden Suites | Notes |
|---|---|---|---|
| Toronto | Up to 4 units | Permitted | Multiplex expansion approved |
| Stratford | Up to 3 units | Permitted | 3 units per lot allowed |
| North Dumfries | Limited | Not as-of-right | Zoning amendment required |
| Hamilton | 4 units | Expanding | Council-approved changes |
| Orillia | 3 units | Concierge support | Fast-track ADU program |
For example:
The City of Toronto amended zoning to allow four residential units in most residential areas.
Stratford permits up to three units per lot as-of-right.
North Dumfries explicitly states garden suites require a zoning by-law amendment.
Orillia has introduced an ADU concierge program to streamline compliance.
Municipal websites and planning departments provide the most current zoning by-law details.
A secondary suite is typically located within the primary dwelling (e.g., basement apartment).
A garden suite (also called an Accessory Dwelling Unit – ADU) is a detached unit located in the rear yard.
Key distinction:
Both may count toward the 3-unit provincial allowance.
Municipal setbacks, lot coverage, and servicing rules often differ.
Some municipalities permit garden suites as-of-right; others require a zoning amendment.
One motivation behind ARU legislation is affordability. In many cases:
Development charges are reduced or exempt.
Municipal programs like Ontario Renovates may offer funding support.
Property taxes may increase after reassessment.
Financial feasibility depends on:
Construction costs
Servicing upgrades
Fire code retrofits
Permit fees
Zoning approval does not guarantee financial viability.
In Orillia, local reporting highlights a fast-track program supporting homeowners who wish to build garden suites or ARUs. The concierge-style process helps navigate:
Permit application steps
Zoning compliance checks
Building Code requirements
This reflects a broader provincial shift encouraging gentle density.
While municipalities like Toronto and Hamilton have approved fourplexes as-of-right, provincial leadership has rejected a blanket Ontario-wide fourplex mandate.
This creates variation across cities. The 3-unit rule remains the minimum guaranteed under provincial legislation, but additional permissions depend on municipal council decisions.
No. “As-of-right” only removes the requirement for a zoning by-law amendment. You must still obtain a building permit and comply with the Ontario Building Code, including fire separation, egress, and safety standards.
In most residential zones across Ontario, up to three residential units are permitted as-of-right. Some municipalities, such as Toronto and Hamilton, allow four units depending on local zoning bylaws.
No. While provincial legislation permits Additional Residential Units, some municipalities still require specific compliance measures or a zoning by-law amendment for garden suites.
The three-unit framework was introduced through amendments under Bill 23 (More Homes Built Faster Act), which modified the Planning Act to require municipalities to permit Additional Residential Units.
Not usually. However, consulting a municipal planner, building official, or experienced professional can help ensure zoning compliance and Ontario Building Code approval.
In many cases, development charges are reduced or exempt for Additional Residential Units, but policies vary by municipality. Always confirm with your local planning department.
Reviewed by Municipal Planning Policy Specialist | Updated 2026
If you’re considering adding a secondary suite, garden suite, or Additional Residential Unit, our team of experienced cottage builders in Ontario can help you.
We assess zoning eligibility, building permit requirements, and Ontario Building Code compliance.
Book a free consultation or call us directly to speak with a qualified expert about your property and next steps.
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