As housing demands continue to grow across the province of Ontario, homeowners and municipal leaders are turning to innovative solutions like additional residential units (ARU) to provide more diverse and affordable living options. With recent changes to the Planning Act, including the introduction of Bill 23 and the Homes Built Faster Act, the path to building an additional residential unit has never been clearer. Whether you live in a single detached, semi-detached, or townhouse dwelling, Ontario now allows multiple residential uses as-of-right in many zones.
This guide covers everything you need to know about ARUs in Ontario—what they are, how they function, and what steps you need to take in 2024 to legally add more units to your residential property.
Understanding the Additional Residential Unit (ARU)
An additional residential unit (also referred to as a second unit, garden suite, or coach house) is a self-contained dwelling unit located on a parcel of urban residential land. Homeowners can build these units within, attach them to, or place them separate from the existing residential unit. Designed as self-contained residential spaces with full living amenities, they often serve as affordable housing, temporary accommodations, or rental units for extended families or tenants.
The Ontario Second Unit Guide confirms that homeowners can legally add up to two additional residential units on a residential lot in many urban residential areas. This can include:
- A basement apartment inside the principal dwelling
- A detached accessory building like a laneway house or tiny home
The creation of ARUs supports the growing need for housing diversity while helping to increase housing supply in settlement areas across the province.
ARUs in Ontario: A Way to Unlock More Housing Supply
The availability of additional housing contributes directly to the housing supply and helps address long-standing housing needs.ARUs help unlock more housing by allowing homeowners to add extra units to their residential lots—especially in areas with limited space for new subdivisions. With proper zoning regulations, ARUs offer a path to improving the number and type of housing units available in established neighborhoods.
The updated Planning Act now directs municipalities to allow additional residential units in existing residential zones and developments. This applies broadly to properties with municipal water and sewage, making many lots eligible for ARU construction by default.
Create an ARU: What Types Are Allowed?
There is more than one type of ARU available for property owners depending on their lot size and zoning by-law. ARUs can be:
- Interior: Within the footprint of the existing residential unit (e.g., basement apartment)
- Attached: An accessory dwelling added to the home’s footprint (side or rear)
- Detached: A detached accessory dwelling unit such as a garden suite, laneway house, or tiny home
Homeowners must design each additional residential unit to meet the Ontario Building Code, follow local by-laws, and comply with building permit regulations. Whether you’re adding one or two units, each dwelling unit must remain self-contained, safe, and in full compliance with building code requirements.
ARU Services and Process for Planning
If you’re preparing to create an ARU, the first step is understanding your municipal zoning regulations and official plan and zoning policies. Here’s a look at the service and planning process:
- Preliminary Review: Evaluate the property’s eligibility based on zone, property lines, and lot area.
- Design Submission: Prepare drawings that demonstrate compliance with Ontario Building Code and zoning by-law rules.
- Obtaining a Building Permit: Submit all documents to your local municipal office. Some projects may also require a minor variance.
- ARU Construction: Begin building on the property once permits are issued. Ensure construction follows all code requirements and floor area limits.
- Final Inspection and Approval: Once built, your additional residential unit will undergo a final review to ensure compliance.
Working with professionals experienced in ARU development ensures a smooth, compliant process.
Ontario’s Housing Strategy and the Push for ARUs
Why is the province of Ontario putting such a strong focus on ARUs? Because the creation of ARUs is a proven way to help:
- Increase housing supply in high-demand communities
- Improve access to rental units
- Reduce urban sprawl by maximizing urban residential land
- Provide affordable housing options in areas close to schools, transit, and services
Backed by strong policies and the Homes Built Faster Act, Ontario is actively streamlining development charges and approval processes for ARUs. These efforts make it easier for homeowners to add additional housing units and help grow local communities.
What You Need to Know
In 2024, there are clear rules for building additional residential rental spaces on your land. The key takeaways include:
- Residential units as-of-right are allowed in most urban zones
- ARUs offer a flexible option for property owners to use their land
- Municipalities must permit additional residential units in compliance with provincial legislation
- Designs must meet the Ontario Building Code and align with your zoning by-law
- ARUs must have safe access, proper water and sewer, and meet floor area and setback requirements
Some municipal water systems may limit the number of ARUs, so always verify with your local planning department.
Building Permit & Code Considerations
Before starting construction, you’ll need to apply for a building permit and prepare your drawings for review. Here’s what you need to consider:
- Confirm your zone allows for the type of ARU you’re building
- Ensure your plan complies with building code requirements, including fire separation, self-contained living, and ventilation
- Confirm whether your ARU is part of an accessory building or added to an existing dwelling
- If your ARU exceeds the allowed floor area, a minor variance may be required
These steps help ensure your ARU project doesn’t get delayed or denied due to compliance issues.
Additional Residential Units Impact
An additional unit adds more than just square footage. These accessory dwelling units offer a variety of benefits:
- Increase property value with new housing units
- Offer flexible housing options for family or rental
- Help meet the demand for residential rental supply
- Provide a path toward long-term affordability in high-growth zones
Whether you’re adding a basement apartment, constructing laneway houses, or planning a full detached build, your ARU represents a smart investment and a sustainable housing solution.
Final Thoughts: Why Additional Residential Units Matter
Adding additional residential units in Ontario is more than a construction project—it’s a forward-thinking approach to meet the growing housing needs of 2024 and beyond. These dwelling solutions support families, offer rental housing, and allow more people to live in neighborhoods they already know and love.
If you want to create an ARU, now is the time. With the right support and a clear understanding of zoning by-law, building permit, and code requirements, your dream of building a legal, functional, and affordable dwelling unit is well within reach.
Ready to start? Our team at ADU Ontario can help guide your ARU development from start to finish.
Reach out to the planning experts today—and let’s create additional housing together.
Frequently Asked Questions – Additional Residential Units in Ontario
1. What are secondary suites and how do they differ from ARUs?
Secondary suites are a type of additional residential unit built inside an existing home, such as a basement apartment. Unlike detached ARUs, secondary suites share the same structure as the main dwelling. Both are self-contained, but secondary suites often follow simpler zoning rules.
2. What do I need for the construction of an additional residential unit?
To build an additional residential unit, you’ll need to meet local zoning by-laws, follow the Ontario Building Code, and often secure a building permit. Each unit on a property must offer safe access, enough space, and proper services like water and sewer.
3. Are residential uses allowed on all types of lots?
Most urban and suburban zones in Ontario allow residential uses as-of-right, which includes ARUs and secondary suites. However, your lot’s zoning classification and size will determine whether you can build one.
4. What should I know about property tax implications when adding an ARU?
When you add an ARU, your property’s value may go up—leading to changes in your annual property taxes. Municipal assessors typically include the new unit in their evaluations, especially if you plan to rent it out.
5. How does additional housing help the economy?
Building more ARUs and secondary suites does more than expand housing—it creates jobs in design, construction, and local trades. This added housing contributes to the economic growth of communities by increasing rental availability and strengthening infrastructure demand.
6. Where can I build an ARU across Ontario?
Many municipalities across Ontario allow ARUs, especially those that have updated their zoning policies to match changes in the Planning Act and provincial guidelines. Check with your local planning department to confirm what’s permitted in your area.