Are You Considering Building an Accessory Dwelling Unit (ADU)?
Are you considering building an accessory dwelling unit? You're not alone. Across Halton and Hamilton, more homeowners are looking at their backyards, basements and garages and seeing the same thing: room for a second home on the property they already own.
An accessory dwelling unit can house a parent, give an adult child a place to launch, create rental income or add long-term value to your property. It's also a real construction project, with rules, costs and design decisions that deserve careful thought. Here's what to know before you start.
What is an accessory dwelling unit?
An accessory dwelling unit is a self-contained home on the same lot as a main house, with its own kitchen, bathroom, sleeping area and entrance. In Ontario you'll also hear the terms additional residential unit, secondary dwelling, secondary suite, in-law suite, garden suite, laneway house and coach house. The names vary by municipality and by type, but the idea is the same: a second, independent home on one property.
The main types of accessory dwelling units
Inside the main home. A basement suite or a converted part of the main floor. This is often the most cost-effective option because the structure already exists. [Basement Renovation Ideas for Burlington Homes]
Attached to the main home. An addition built with its own entrance and living space, connected to the house but separated from it by fire-rated construction.
Detached in the backyard. A standalone garden suite or backyard home. It offers the most privacy for both households and the most design freedom.
Above or in place of a garage. A coach house or laneway house, often built where a garage sits today or facing a rear lane.
What Ontario now allows
Provincial changes in recent years have made accessory dwelling units much easier to build. On many residential lots with full municipal services, Ontario now allows up to three residential units: for example, a main home, a unit inside it, and a detached unit in the backyard.
Each municipality still sets the details through its zoning bylaw, including setbacks, height, lot coverage, parking and servicing. That means the rules in Burlington, Oakville, Milton, Halton Hills and Hamilton can differ. The first step for any project is confirming what your specific lot allows.
Why homeowners are building them
Family. Aging parents can live independently, close to the people who care about them. Adult children can save for a home of their own.
Income. A rental unit can offset mortgage costs or provide income in retirement.
Flexibility. A unit that houses a parent today can become a rental, a guest house or a home office later.
Downsizing without leaving. Some homeowners move into the smaller unit themselves and rent or give the main house to family.
How the process works
Feasibility. Confirm zoning, lot size, setbacks, servicing and access for your property.
Design. Plan the layout, size, privacy and relationship to the main house.
Pricing. Develop a detailed budget based on the actual design and site.
Permits. Apply for a building permit, plus any zoning approvals if your project needs them.
Construction. Build the unit, connect services and complete inspections.
Occupancy. Final inspections confirm the unit is ready to live in.
What affects the cost
Cost depends mostly on type. A unit inside an existing basement is usually the least expensive, and a detached unit is usually the most, because it needs its own foundation, structure, roof and utility connections. Other factors include size, servicing distances, site access for construction, finish level and any upgrades the main house needs to support a second unit.
Provincial changes have also reduced or removed some municipal development charges for additional units in many cases, and federal programs have been introduced to help homeowners finance secondary suites. Ask your builder and your lender what currently applies.
Frequently Asked Questions
Do I need a permit to build an accessory dwelling unit?
Yes. Every accessory dwelling unit needs a building permit, and some need zoning approvals as well. A permitted unit protects your safety, your insurance coverage and your resale value.
Can I rent out an accessory dwelling unit?
In most cases, yes, as long as the unit is built with permits and meets the Ontario Building Code and fire code. Rules on short-term rentals vary by municipality.
Can I sell an accessory dwelling unit separately from my home?
In most cases, no. An accessory dwelling unit is part of the same property as the main home. Separating ownership would require a separate legal process, which is uncommon for these units.
Does an accessory dwelling unit add value to my home?
It often does, especially when it's built with permits and designed well. A legal second unit can appeal to buyers looking for rental income or room for family.
Which type of accessory dwelling unit is right for my property?
It depends on your lot, your budget and who will live there. A site visit is the fastest way to narrow the options.
Thinking about an accessory dwelling unit?
The best accessory dwelling units start with a clear feasibility check and a design that works for both households. If you're considering one in Burlington, Oakville, Milton, Halton Hills or Hamilton, we'd be glad to look at your property with you.
