If you're a London, Ontario homeowner thinking about adding a backyard suite, a basement apartment, or a detached unit, the permit process is usually the part that feels the most intimidating. The good news: Ontario's rules around additional residential units (ARUs) have loosened considerably in recent years, and London has adopted broader housing-unit policies that make these projects more achievable than they were even a few years ago.
This guide walks through every stage of getting an ARU permit in London Ontario — from your first zoning check to your final occupancy sign-off — with a realistic timeline and the common reasons applications stall.
ADU vs. ARU: a quick definition
You'll see both terms used, sometimes interchangeably.
- ARU (Additional Residential Unit) is the term Ontario and the City of London use in policy. It covers a self-contained dwelling unit added to a property — a basement suite, a unit inside the main house, or a detached structure.
- ADU (Accessory Dwelling Unit) is the more common North American term, often used for detached backyard units, sometimes called "garden suites."
For permitting purposes in London, what matters is whether your unit is inside the existing home, attached, or detached — because the requirements differ. (For a broader overview, see our complete ADU guide.)
Step 1: Confirm zoning and lot eligibility
Before you fall in love with a floor plan, confirm your lot can legally support an additional unit.
Ontario's More Homes Built Faster Act allows up to three residential units on many serviced residential lots as-of-right, and London has adopted bylaws that expand housing options across neighbourhoods. That said, local details still govern your specific property, including:
- Lot size and frontage
- Setbacks from property lines
- Maximum building height and footprint (lot coverage)
- Parking requirements
- Servicing (water, sewer, hydro capacity)
London's rules continue to evolve — some policies have been adjusted, reviewed, or paused as council works through caps and limitations. Always confirm the current zoning rules for your exact address with the City of London before committing. A pre-application or zoning verification inquiry is the cleanest way to do this.
Step 2: Choose your unit type and design
Your design needs to satisfy both the Ontario Building Code and London's zoning rules. This is where decisions about a custom design versus a pre-designed model matter.
A pre-designed model can shorten this stage considerably because the layout, structure, and code details are already worked out. At Kuzyn Builds we offer three detached models with published fixed starting prices:
You can compare all three on our ADU models page. Because our detached models carry Tarion warranty coverage, the design and documentation are built to a standard that supports a smoother permit submission.
Step 3: Prepare your permit application
A building permit application for an ARU in London typically requires:
| Document | What it shows | |---|---| | Site plan | Unit location, setbacks, lot coverage, parking | | Architectural drawings | Floor plans, elevations, sections | | Structural drawings | Foundation, framing, load paths | | Mechanical/HVAC details | Heating, ventilation, energy compliance | | Plumbing & electrical | Fixture layout, servicing connections | | Grading/servicing plan | Drainage and utility connections (often required) |
Missing or inconsistent drawings are the single most common reason applications get delayed, which is why a builder who handles documentation matters.
Step 4: Submit and pay fees
You submit your application to the City of London's building division, usually through their online portal. Fees include the building permit fee and may include development charges or other levies depending on the project and unit type.
Fees and any applicable grants or rebates change from year to year. Federal and provincial programs supporting secondary suites have come and gone and been revised, so verify the current amounts and eligibility directly with the City and the relevant program before you budget. Don't rely on a number you read in an older article — including this one.
Step 5: Plan review and permit issuance
Once submitted, the City reviews your application against the Building Code and zoning. If reviewers find deficiencies, they issue comments and you (or your designer) respond with revisions. A clean, complete first submission moves through far faster than one that triggers multiple rounds of comments.
When everything checks out, the permit is issued and you can begin construction.
Step 6: Construction and inspections
During the build, the City conducts inspections at key stages — typically footings/foundation, framing, insulation/vapour barrier, plumbing, electrical (ESA handles electrical separately), and final. Each stage must pass before you proceed.
This is where hands-on craftsmanship pays off. Work that's built right the first time clears inspections without rework.
Step 7: Occupancy
Once the final inspections pass, you receive occupancy approval, meaning the unit is legally habitable. For our detached models, this is also where Tarion warranty protection becomes valuable — giving you and any future tenants documented new-build coverage.
A realistic timeline
Every project differs, but here's a reasonable planning framework for a detached ARU in London:
| Stage | Typical duration | |---|---| | Zoning check + feasibility | 1–3 weeks | | Design + drawing package | 3–8 weeks (faster with a pre-designed model) | | Permit submission + review | 4–12 weeks (varies with completeness and City workload) | | Construction | 3–6 months depending on model and site | | Inspections + occupancy | Built into construction; final sign-off at the end |
In short: from first inquiry to occupancy, plan for roughly 6 to 12 months. A pre-designed, permit-ready model trims time off the front end.
Common reasons applications stall
In our experience, delays usually trace back to a short list of issues:
- Incomplete drawings — missing structural or servicing details trigger comment rounds.
- Zoning mismatch — a design that exceeds height, coverage, or setback limits.
- Servicing constraints — water, sewer, or hydro capacity that needs upgrading.
- Grading and drainage — overlooked stormwater management.
- Parking — not meeting the required spaces for the additional unit.
- Policy changes mid-process — because London's rules are still being refined, confirm current requirements rather than relying on last year's understanding.
Choosing an experienced local builder who knows London's process — and who submits complete, accurate packages — is the most reliable way to avoid these.
How Kuzyn Builds helps
We're a family-owned construction company based in London, serving the city and nearby communities including St. Thomas, Woodstock, Stratford, and Strathroy. We build custom homes, ARUs, multi-unit projects, and renovations. For ARUs specifically, our published fixed starting prices, named pre-designed models, and Tarion-warranted detached units are designed to make the path from idea to occupancy as predictable as possible.
If you want to understand the broader market first, our ADU builders buyer's guide walks through how to evaluate any builder, and our services page covers everything we do.
Frequently asked questions
Do I need a permit for a basement or backyard unit in London?
Yes. Any self-contained additional residential unit requires a building permit and must comply with the Ontario Building Code and London's zoning rules. Skipping permits creates safety, insurance, and resale problems.
How long does an ARU permit take in London, Ontario?
Plan reviews commonly run several weeks to a few months depending on how complete your submission is and the City's current workload. A clean, complete package with a pre-designed model is the fastest route.
Are there grants or rebates for building an ARU?
There have been federal and provincial programs supporting secondary suites, but they change and are periodically revised. Confirm what's currently available and what you qualify for directly with the City of London and the relevant program before budgeting.
Can every property in London add an ARU?
Many serviced residential lots can, thanks to provincial and city policy changes — but lot size, setbacks, servicing, and parking still govern your specific address. Always verify zoning for your exact property first.
Ready to start?
The permit process is far less daunting with the right team handling the details. If you're weighing an ARU on your London property, we'll help you check feasibility, choose a model, and move toward a smooth approval.
Contact Kuzyn Builds for a free consultation or call (519) 694-4776 to talk through your project.
This article is general information, not legal or regulatory advice. Bylaws, fees, and programs change — confirm current requirements with the City of London before you build.