Building an ADU in London, Ontario: A Homeowner’s Guide
- John Barnhart
- Sep 22
- 3 min read
If you live in London, Ontario, you’ve probably heard the buzz around Additional Residential Units (ARUs) — also called ADUs, secondary suites, or basement apartments. With housing demand rising and updates to Ontario’s 2024 Building Code, adding an ADU has become one of the most practical ways to:
Generate rental income
Create space for family or multi-generational living
Boost your property value
But how do you actually get an ADU approved in London? Here’s a step-by-step guide every homeowner should know.
What Is an ADU in London?
An ADU in London, Ontario is a self-contained dwelling on the same lot as your main home. It must include its own kitchen, bathroom, and sleeping area.
Common ADU types include:
Basement suites (secondary units within an existing house)
Attached units (side or rear additions)
Detached garden suites or coach houses (in converted garages or new backyard structures)
Step 1: Check Zoning with the City of London
Not every property qualifies for every type of ADU. Some lots allow detached backyard units, while others only permit basement or attached suites.
👉 Always confirm with the City of London for the most up-to-date zoning rules. This will tell you what’s possible on your property before you move forward.
Step 2: Design Your ADU to Meet the Ontario Building Code
Once you know your property qualifies, the next step is creating a design that complies with the 2024 Ontario Building Code. Key requirements include:
Basement Ceiling Height: Basement ADUs must have at least 6′5″ (1.95 m) clear height over most living areas, with a reduced clearance of 6′1″ (1.85 m) permitted under beams, ducts, and stairways.
Self-contained facilities: Each unit must have its own kitchen, bathroom, and sleeping space.
Fire and safety: Proper exits, fire separations, and ventilation are mandatory for approval.
These details are what City staff will review when you apply for a building permit.
Step 3: Apply for a Building Permit in London
You’ll need a building permit before starting any ADU construction. Your application must include:
A site plan showing where the ADU fits on the lot
Floorplans and elevations of the unit
Code-compliant details for structure, fire safety, plumbing, and HVAC
Incomplete or non-compliant drawings are the number one reason permits are delayed.
Step 4: Build and Pass Inspections
Once your building permit is approved, construction can begin. The City of London will carry out inspections at key stages — framing, insulation, plumbing, electrical, and final occupancy.
When everything matches the approved plans and passes inspection, you’ll receive an occupancy permit, making your ADU legal and ready to use.
Why Work with a BCIN Designer in London?
Most homeowners don’t realize that professional drawings are mandatory for an ADU building permit. A BCIN-certified designer ensures your application is done right the first time.
At The Building Permit Guy, we:
Create professional drawings that meet both zoning and Building Code standards
Handle your building permit application and respond to City comments
Support you during construction if inspectors request revisions
Save you time, money, and frustration by working with the City on your behalf
Ready to Start Your ADU Project in London?
If you’re planning a basement suite, secondary unit, or coach house in London, Ontario, here’s your action plan:
Check zoning with the City of London.
Contact The Building Permit Guy. We’ll prepare BCIN-stamped drawings that meet the 2024 Ontario Building Code.
Build with confidence knowing your ADU will pass review and inspections.
👉 Reach out today to start your ADU project in London, Ontario.
