Garden Suites in London, Ontario: Four Units, Two Out Back
London allows up to four units on a house lot, and up to two of them can be in a detached building. No extra parking is required. The catch: every rental unit needs a City licence, bedroom counts are capped, and an interim control by-law is limiting unit size while appeals run.
At a glance
The ARU Loan is repayable, not a grant. London’s forgivable construction grants closed in 2026 with all funds allocated.
Yes. London permits up to three additional residential units on a house lot, four units total, and up to two can be in a detached building in the rear or interior side yard. No extra parking is required. While appeals run, an interim control by-law caps each unit at 80% of the main house’s floor area, and each unit gets at most two bedrooms. Rental units need a City licence.
We Don’t Build in London. Here’s what we can do.
We are a builder based in Tiny Township, a few hours up the road. We build garden suites in Simcoe County and around Georgian Bay through ICFhome.ca. Outside Simcoe, we sell lot reports, permit packages and builder calls. We are not going to drive a concrete truck down the 401 for you.
We have built 300+ custom homes since 1979. London’s rules are more generous than most Ontario cities, which is good news. It also means more people try it, and more of them get stung by the parts nobody mentions: the rental licence, the bedroom cap, the drainage review and the interim control by-law.
What London calls it
London uses Additional Residential Unit (ARU). A detached one is a “detached ARU”. The City lists four types: interior or basement conversion, converted garage, detached, and an addition to the existing building. If you search london.ca for “garden suite” you will mostly come up empty. Search “ARU”.
What You Can Build in London
These are the numbers the City publishes on its ARU page. Height and setbacks for detached ARUs sit in Section 4.37 of the Zoning By-law, and the City does not repeat them on the page.
| Rule | London (as published) |
|---|---|
| Where allowed | Where zoning permits single detached, semi-detached, duplex, triplex, converted or street townhouse dwellings |
| Units per lot | Max 4 total including the original; max 3 ARUs; up to 2 ARUs in a detached building |
| Size | ARU gross floor area max 80% of the main dwelling’s GFA (Interim Control By-law CP-1600-300) |
| Bedrooms | Max 2 per ARU; max 3 combined in accessory buildings; max 3 combined in or attached to the house; max 5 across all ARUs |
| Minimum size | Bachelor ARU 17.5 m² (Ontario Building Code) |
| Location | Rear or interior side yard only; not in the front yard or between the house and the street on a corner lot |
| Height and setbacks | Not published on the ARU page — Zoning By-law Section 4.37 |
| Drainage | Not in a swale or overland flow route; keep existing drainage; downspouts not onto neighbours |
| Parking | No additional parking required; no additional driveways allowed |
| Severance | May be possible in settlement areas, reviewed case by case |
Last checked October 2026 · Source: City of London, Additional Residential Units
The interim control by-law, in plain English
In October 2024 London put its four-unit rules in force. Council later passed a permanent amendment on March 3, 2026, and it was appealed. Until those appeals are resolved, Interim Control By-law CP-1600-300 applies, and it is the source of the 80% floor area cap.
What that means for you: if your house is 120 m², a detached ARU can be up to 96 m², but the number could change when the appeals finish. Design to today’s rule and get the zoning review done before you order trusses.
The general accessory building rules do not apply
London’s Section 4 general provisions cap ordinary accessory buildings at 4.0 m tall, 10% of the lot, and 0.6 m from the side and rear lines. Subsection 4.1(7) says plainly that detached ARUs are not subject to those three rules; Section 4.37 governs them instead. So don’t let a neighbour tell you the 4.0 m shed limit kills your two-storey suite. Ask zoning for the Section 4.37 numbers for your zone.
Two units in one backyard building
Up to two ARUs can share a detached building, but bedrooms across all accessory-building units are capped at three combined. Two one-bedroom units out back is fine. A two-bedroom and a one-bedroom is the limit. Plan the layout around the bedroom cap, not the square footage.
How a London ARU Permit actually goes
London publishes more of the process than most cities. Here it is in order, with the fees that are published.
Confirm zoning
Check your zone on the City’s map and confirm with zoning@london.ca or 519-930-3510. Ask specifically for the Section 4.37 detached ARU limits for your lot.
Confirm servicing
The City asks you to confirm water and sewer can take the added demand: 519-930-3500 or PlanDev@london.ca. Gas and hydro are London Hydro and Enbridge, not the City.
Prepare drawings
Scaled site plan showing setbacks, lot coverage, landscaped open space and the sewer connection; scaled construction drawings (no single-line drawings); Schedule 1 designer form. HVAC must be designed by a BCIN-qualified designer, and roof trusses stamped by an engineer.
Apply for the permit
Review period is 15 business days. Applications based on a CMHC catalogue design are reviewed within 10 business days. The fee depends on size and building type; the City does not publish a flat ARU rate.
Build, inspect, handle grading
Lot grading is reviewed; questions go to stormwater@london.ca. If the house is less than five years old, its original permit must be closed first.
Get the rental licence
Every ARU needs a Residential Rental Unit Licence: $175 to apply, $171 for the fire inspection, $65 a year to renew. Property standards and fire inspections happen before the licence is issued.
Last checked October 2026 · Sources: London ARU page, Residential Rental Unit Licences
The licence is not optional, and it is not just for students. London requires a building permit and a rental unit licence for all ARUs. If you rent to anyone, including through a lease to a relative, ask the City whether your situation needs one. The ARU Loan also requires a valid licence renewed every year.
Development Charges, Loans and the grants that closed
Development charges. The City says the Province has exempted certain ARUs from development charges, subject to conditions, and asks you to confirm with building@london.ca. Under the Development Charges Act, a qualifying second unit in an ancillary building is exempt where the main house has no more than two units. A third or fourth unit can be a different story, so ask before you add the second backyard unit. Our development charges guide has the plain-English version.
The grants closed. London ran ARU Construction Grants in 2026: $20,000 with no rent cap, $45,000 for units held at or below 100% of CMHC Average Market Rent, and a $45,000 Indigenous stream. Permits had to be issued between April 29 and September 7, 2026, and the City now says all funding is allocated. A separate $20,000 grant for builders of new homes also closed.
The ARU Loan is still listed. It is the lesser of $45,000 or the cost of eligible work, for any ARU type at any rent. It is repaid over 108 equal monthly payments starting a year after the advance. The page lists no interest rate. Conditions include an owner-occupied main house, a valid rental licence renewed every year, leases of at least 31 days (no short-term rental), and approval before work starts.
| Program | Amount | Key conditions | Status (Oct 2026) |
|---|---|---|---|
| ARU Construction Grant | $20,000 | Owner’s primary residence; 10-year rental; lien on title | Closed, funds allocated |
| Affordable ARU Construction Grant | $45,000 | Rent at or below 100% CMHC AMR; 10 years | Closed, funds allocated |
| Indigenous ARU Construction Grant | $45,000 | No rent cap; owner-occupancy not required | Closed, funds allocated |
| ARU Construction Grant for New Homes | $20,000 | Builders, new unoccupied single detached | Closed, funds allocated |
| ARU Loan | Lesser of $45,000 or eligible cost | Repayable, 108 monthly payments; licence; no short-term rental | Listed, no closing date shown |
Last checked October 2026 · Source: City of London Community Improvement Incentives
Read the grant terms before you wish they were still open. The forgivable grants were registered on title as a loan at 8% annual interest, compounded every 30 days, forgiven only if you complied for the full term. Sell or breach early and it comes due. That is fair for public money, but it is not free.
Using a CMHC catalogue design in London?
The catalogue gets you a near permit-ready building. Our Urban Pre-Approved Wrapper adds the site plan, grading coordination, forms and heat loss London asks for. From $1,499.99 + HST, fixed quote first.
London Accepts the CMHC Housing Design Catalogue
London does not run its own plan catalogue. Instead, the City supports all Ontario-region designs in the CMHC Housing Design Catalogue, and reviews catalogue-based permit applications within 10 business days instead of 15.
The City calls them “near permit-ready,” and that word “near” is doing real work. A qualified professional still has to adapt the design to your lot. That means a site plan, grading, the sewer and water connection, the HVAC design by a BCIN holder, and engineered trusses. The building is the easy half. See our pre-approved plans round-up for what catalogue plans leave out.
London also mentions shipping-container units: allowed, but a professional engineer must design the unit, foundation included. If you have seen a bargain container suite on social media, ask what the engineering, foundation and servicing added.
Water Goes Downhill. So does your budget.
- Capacity is checked, not assumed. London asks you to confirm water and sewer can handle the added demand. Two units out back plus a house is a lot of fixtures on one lateral.
- Connections go through the house or to the street. The City says connections are generally made through the existing dwelling or directly to the street. A long run across a deep lot, under a driveway, is real money. Get the lateral depth before you set the suite’s floor.
- Drainage is a permit item. A detached ARU cannot sit in a swale or overland flow route and cannot push water onto the neighbours. Lots with a rear-yard swale can lose a lot of buildable space to this rule.
- Utilities are not the City. Hydro is London Hydro and gas is Enbridge. A new service or a meter for the suite is their timeline, not the building department’s.
Rural lots outside London’s urban boundary are a different conversation. If a septic system is involved, the design has to come from a qualified designer; we send that work to SepticReplacement.ca. For the BCIN-stamped heat loss and HVAC design London requires, see OntarioHeatLoss.ca.
Common Mistakes in London
Designing to bedrooms, not to the cap
Three bedrooms in one backyard unit is over the two-per-ARU limit. Draw the bedroom count first.
Ignoring the interim control by-law
The 80% floor area cap is in force until appeals are resolved. A suite sized to a rumour about the permanent by-law may not get a permit.
Adding a driveway
No extra parking is required, and no additional driveway is allowed. Don’t design a second curb cut into your plan.
Skipping the rental licence
$175 plus $171 for the fire inspection is cheap compared with a by-law order on an unlicensed unit.
Building in the swale
The flat spot at the back of the yard is often where the water goes. The City checks. Your neighbour’s basement will too.
Counting a closed grant
The 2026 construction grants are fully allocated. If your budget needs $45,000 of free money, it needs another look.
Rules of thumb before you spend a dollar
- Ask zoning for the Section 4.37 detached ARU limits for your zone, in writing.
- Measure your house’s gross floor area. 80% of it is your current ceiling.
- Walk the yard after a heavy rain. Where the water runs is where the suite can’t go.
- Confirm sewer and water capacity with the City before you pay for drawings.
- Price the servicing before the building. Our servicing cost guide and cost calculator help.
Find out what fits on your London lot in 48 hours.
The $399 + HST Garden Suite Feasibility Report checks zoning, bedroom and size caps, drainage, servicing and the permit path for your address. The fee is credited toward permit plans.
London Garden Suite FAQ
Can I build a garden suite in London, Ontario?
Yes, where zoning permits single detached, semi-detached, duplex, triplex, converted or street townhouse dwellings. London allows up to three additional residential units and four units total per lot, and up to two of those ARUs can be in a detached building in the rear or interior side yard.
How big can a detached ARU be in London?
While appeals to the March 3, 2026 permanent amendment are resolved, Interim Control By-law CP-1600-300 limits an ARU to 80% of the main dwelling’s gross floor area. Each ARU can have at most two bedrooms, and the minimum bachelor unit under the Building Code is 17.5 m2. Height and setbacks are in Zoning By-law Section 4.37.
Do I need parking for a garden suite in London?
No. London requires no additional parking for ARUs. It also does not allow an additional driveway to serve an ARU, so plan to use the existing driveway or street parking.
Do I need a rental licence for an ARU in London?
The City says a building permit and a residential rental unit licence are required for all ARUs. A new licence costs $175 to apply plus $171 for the fire inspection, and $65 a year to renew. Property standards and fire inspections are done before the licence is issued.
Is there a garden suite grant in London in 2026?
The 2026 ARU Construction Grants of $20,000 and $45,000 are closed and fully allocated. The ARU Loan is still listed: the lesser of $45,000 or eligible costs, repaid over 108 monthly payments starting one year after the advance, with an owner-occupied house and a valid rental licence required.
Do garden suites in London pay development charges?
The City says the Province has exempted certain ARUs from development charges, subject to conditions. A qualifying second unit in an ancillary building is exempt under the Development Charges Act. Confirm your project with building@london.ca or 519-661-4555 before you budget, especially for a third or fourth unit.
Can I use a CMHC catalogue design in London?
Yes. London supports all Ontario-region designs in the CMHC Housing Design Catalogue and reviews catalogue-based permit applications within 10 business days. A qualified professional still has to adapt the design to your lot, including site plan, grading, servicing and BCIN HVAC design.
How long does a London ARU building permit take?
London lists a 15 business day review period for a building permit, or 10 business days for applications based on a CMHC catalogue design. Incomplete applications take longer, so submit a full package with scaled drawings, a site plan and the Schedule 1 designer form.
Will you build my garden suite in London?
No. We build in Simcoe County and around Georgian Bay. For London we sell the $399 + HST feasibility report, permit packages and paid builder calls, so you can hire a local builder with a checked lot and a clear scope.