Additional Dwelling Units: Ontario Guide 2024

Additional Dwelling Units: Ontario Guide 2024

Are you eligible for an additional dwelling?

Many Ontario property owners consider adding some form of secondary living spaces on their property.  These spaces are known as Additional Dwelling Units, or simply ADUs.  These units are gaining in popularity, so interested parties may be curious about the types of ADUs, the benefits of ADUs, and all the code and regulations that are implicated when converting or constructing a secondary structure.  

What Are ADUs? 

ADUs, are self-contained residential units located on the same property as a single-family home. These units can be attached to the main house, such as a converted garage or basement, or they can be a separate, standalone structures and accessory buildings on the property, such as a small cottage or apartment.

ADUs provide homeowners with a flexible and cost-effective way to add additional housing to their property. They can be used to accommodate aging parents, adult children, or renters, providing a separate and private living space while still being connected to the main house. Additionally, ADUs can be a source of rental income for homeowners, providing a way to offset mortgage costs and increase property value.

Types of ADUs

Types of ADUs include many forms of secondary suites/secondary dwelling units.  As general categories, these structures come in the form of attached, detached, and semi-detached.  Attached ADUs occur when property owners convert existing spaces such as basements into new uses.  While other structures built nearby, but separate from,  the main living space are detached. 

  • Basement Apartments: These are living spaces located in the basement of a residential property, typically with a separate entrance. 
  • Detached Garages: These are standalone structures separate from the main house, designed to store vehicles and sometimes used for storage or as a workshop. 
  • Carriage Houses and Coach Houses: Historically, these were outbuildings on large estates used to store horse-drawn carriages and related equipment. Today, they are often converted into living spaces, guest houses, or rental units while retaining some of their original architectural charm.
  • In-law Units (In-law Suites, In-law Flats): These are separate living spaces within a single-family home, designed to accommodate relatives such as parents or in-laws. 
  • Laneway House / Laneway Suites: These are small, detached housing units built in the backyards or along laneways of existing properties. 
  • Garden Suite: Similar to laneway houses, garden suites are secondary dwellings located in the backyard of a primary residence. They offer self-contained living spaces and are increasingly popular as a means to increase housing density in urban areas while maintaining the character of residential neighborhoods.

Are you eligible for an additional dwelling?

Where Can you Build ADUs?

In Ontario, ADUs can be built on in almost any "parcel of urban residential land" - including within detached dwellings, semi-detached dwellings, or a townhouses. Bill 23 introduced a new way to define "parcel of urban residential land." It basically means land in an area where local laws permit residential housing and, and where there's access to city water and sewer services.

National and Provincial legislators have encouraged the building of ADUs and eased regulations regarding their location. The Ontario Helping Homebuyers, Protecting Tenants Act recognized the need for a housing supply action plan, to open up more affordable units for rent.  Furthermore, the Ontario Planing Act requires all cities to allow ADUs in their zoning by-laws and Official Plans. The ACT sets out minimums that every municipality must allow in their zoning by-laws:

  • You can have two additional living spaces within your house as long as there's only one additional living space in any other building on the property.
  • You can have three total living spaces within your house but only if there are no living spaces in any other buildings on the property.
  • You can have one living space in a separate building on the same property as your house, but only if the main house has up to two living spaces and there are no living spaces in any other separate buildings.

Toronto Fourplex Law

The city of Toronto relaxed their zoning laws to allows for the construction and/or conversion of residential property in the city to create up to four residential units. This change was intended to provide an opportunity for increased housing density within the city. and address the growing demand for affordable housing options in Toronto by encouraging the development of additional dwelling units. 

Benefits of ADUs

From a societal perspective, ADUs can help to address housing shortages and affordability issues in many communities. They offer a wide range of personal and economic benefits for both homeowners and tenants seeking affordable rental housing. 

One of the key advantages of Additional Dwelling Units is their ability to provide additional income for homeowners. By renting out the ADU, homeowners can generate a steady stream of rental income, which can help offset the costs of their mortgage or other expenses. ADUs can be used for a variety of other purposes, such as housing aging parents, providing a home office or studio space, or accommodating adult children who need temporary housing

ADUs also provide a great housing option for renters. These units are typically more affordable than traditional apartments or single-family homes, making them an attractive option for individuals or small families who are looking for a place to live. Additionally, the close proximity of ADUs to the main residence can create a sense of community and support for renters, as they have the opportunity to build a relationship with the homeowner. 

Are you eligible for an additional dwelling?

In Ontario, building an Accessory Dwelling Unit (ADU) like a basement apartment, laneway house, or in-law suite involves navigating various legal and regulatory requirements. A lawyer can be instrumental in ensuring compliance with zoning laws, building codes, and municipal bylaws, which often have specific provisions governing ADU construction and occupancy. They can help homeowners understand the legal implications of ADU development, such as property tax implications, rental regulations, and potential liability issues.

Moreover, a lawyer can assist in obtaining necessary permits and approvals from local authorities, drafting contracts with contractors or tenants, and addressing any disputes that may arise during the construction process. With their expertise in real estate law and local regulations, a lawyer can provide valuable guidance and representation, helping homeowners navigate the complexities of ADU development in Ontario - safeguarding their interests throughout the project.

Zoning and Building Regulations for ADUs in Ontario

Zoning regulations dictate how a property can be used and developed, while building regulations ensure that the construction of the ADU meets safety and structural standards when building accessory structures.

In Ontario, zoning regulations vary by municipality, and homeowners should check with their local government to determine the specific rules that apply to ADUs in their area.  A lawyer who specializes in local real estate law can assist you when navigating zoning regulations and hearings.

Typical zoning by-law provisions to look for:

  • Parking requirements for ADUs
  • Height restrictions in the subject zone
  • General regulations such as entrances, and access to the street
  • Access to services

In Ontario, building regulations are governed by the Ontario Building Code, which sets out the minimum standards for construction and design.

When building an ADU, homeowners must ensure that the unit complies with all relevant building code requirements, including those related to fire safety, structural stability, and accessibility. This often requires obtaining a building permit from the local government and working with a qualified designer such as an architect or contractor to ensure that the ADU meets all applicable regulations. When prepared, submit the plan to your local municipality's building department. Expect some building permit fees when budgeting planning the cost.

There are several section of the Ontario Building Code that apply:

9.4 – Structural Requirements
9.5 – Design of Area, Spaces and Doorways
9.7 – Windows, Doors and Skylights
9.8 – Stairs Ramps, Handrails and Guards
9.9 – Means of Egress
9.10 – Fire Protection
9.11 – Excavation
9.31 – Plumbing Facilities
9.32 – Ventilation
9.33 – Heating and Air-Conditioning

Overall, creating an ADU is achievable for many homeowners. However, it is important to understand that there are many steps to satisfy all the legal clearances and permits necessary.

Are you eligible for an additional dwelling?


As the demand for housing continues to grow and urban space becomes more limited, ADUs are likely to become an increasingly popular and viable solution for addressing housing needs in many communities. Whether as a way to provide affordable housing options, create additional income streams, or simply accommodate changing family dynamics, ADUs offer a versatile and practical housing solution for homeowners and renters alike.  However, conversion and construction is fraught with regulations, zoning issues, and permits that typical homeowners may not have much experience with.  Many homeowners benefit from the advice of an experienced real estate lawyer.  That way, you have someone on your side, with only your interests in mind, when communicating with the local officials, contractors, and potential renters.

Contact Us

If you have questions about building an Additional Dwelling Units, or any other real estate legal matter, we're here to help. As real estate law specialists, our mission is to provide the clarity and direction you need to protect your property rights.

Contact us today to schedule a free consultation.

Written by
Zachary Soccio-Marandola
Real Estate Lawyer

Direct: (647) 797-6881

Free Consultation

Frequently Asked Questions (FAQ)

Can I build a second dwelling on my property in Ontario?

Yes, additional dwellings are permitted in almost any residential area in Ontario. Check local zoning for details or contact your real estate lawyer.

What is considered a dwelling in Ontario?

A dwelling unit is a living space kept by one or more people as a single housekeeping unit.

Can I have an ADU in Ontario?

Yes. In fact, the Planning Act mandates that all municipalities allow some ADUs in their zoning regulations. Check your local by-laws for the exact regulation or contact a real estate lawyer.

What is the new fourplex law in Toronto?

In response to a shortage in housing units, the Toronto government eased zoning requirements to allow up to four units in a single building in all residential neighbourhoods of the city.