What your backyard needs to fit a garden suite.
A garden suite is new construction, so the rules are less about the structure itself and more about where it can sit and how it connects to services. Your zoning by-law sets the footprint, setbacks, height and lot coverage; the Building Code adds fire rules for walls near the lot line; and servicing has to reach it. Under all of them, your property has to be zoned for one.
Pace out the yard. See what fits.
- Footprint50 m² is within Hamilton’s 75 m², if the house is at least that big.Fits
- SetbacksSits at least 1.2 m from the side and rear lot lines.Fits
- Lot coverageBuildings cover 28% of the rear yard. Hamilton caps total lot coverage at 45%, house included.Fits
- HeightDesigned under Hamilton’s 6.0 m height limit.Shown on the plans
- ServicingIts own water, sewer and hydro, on a servicing plan with the permit.Shown on the plans
Worked example using the City of Hamilton’s rules (Zoning By-law 05-200, Section 4.33), not your by-law. Every municipality sets its own numbers, and trees, easements and the zoning path can change the answer.
The yard can look big and still not fit.
- 01
Setbacks
You can’t build right to the lot line.
- 02
Coverage
The lot can only hold so much building area.
- 03
Servicing
Water and sewer routes can change the design.
What each one actually means.
Size, setbacks, height and coverage come from your municipality’s zoning by-law, so there’s no single Ontario number. We show the City of Hamilton’s rules as a worked example; your city page has yours. The wall rule comes from the Ontario Building Code and applies everywhere. Sources: City of Hamilton Zoning By-law 05-200, Section 4.33; Ontario Building Code (O. Reg. 163/24), Division B, 9.10.15; as of October 2026.
- 01
Footprint
Maximum floor area of the suite itself.
LimitSet by your zoning by-law. Hamilton: up to 75 m², or the house’s floor area if smaller.
- 02
Setbacks
Minimum distance from the suite to the property line.
LimitSet by your zoning by-law. Hamilton: 1.2 m from the side and rear lot lines, 4.0 m from the house.
- 03
Height
Maximum height of the structure.
LimitSet by your zoning by-law. Hamilton: 6.0 m.
- 04
Lot coverage
How much of the lot the house, the suite and other buildings can cover together.
LimitSet by your zoning by-law. Hamilton: 45% of the lot on urban lots.
- 05
Walls near the lot line
Building Code fire rules for a wall facing a property line (spatial separation).
LimitAt 1.2 m or more, window area up to the distance squared. Closer, a 45-minute wall with less glass; under 0.6 m, also noncombustible cladding.
- 06
Servicing
Connection to municipal water, sanitary sewer and hydro.
LimitWater, sewer and hydro run to the suite, shown on a servicing plan. Some municipalities, like Hamilton, require them to connect through the main house.
Will a garden suite fit on my lot?
It depends on your setbacks and lot coverage, which set the legal building envelope in your backyard. A garden suite doesn’t fail on ceiling height the way a basement can. It’s new construction, built to whatever size fits. What it can fail on is fit: a narrow or shallow backyard, mature trees near the build zone, or a rear yard already partly covered by a garage or shed can all eat into the buildable envelope before design even starts.
What services and zoning does a garden suite need?
Its own water, sanitary sewer and hydro connections, and a zoning path that allows it. They’re the two requirements people underestimate.
How do utilities reach the suite?
Unlike a basement apartment, a garden suite needs new water, sewer and hydro lines trenched across the yard. Where they connect is set locally: Hamilton requires them to run through the main house. Submitted as a servicing plan alongside the permit drawings, it’s the single biggest reason garden suites cost two to three times what a basement conversion costs at a similar size.
A clean utility route is a big advantage.Is the unit allowed here?
Ontario’s provincial framework requires most residential lots on municipal water and sewer to allow a garden suite as-of-right: no rezoning or committee hearing for a basic setup. But as-of-right covers the use itself. Setbacks, height, coverage, parking and tree protection are still set locally, and some garden suites were approved under older, temporary-use bylaws instead. The two paths lead to different permit processes.
Check the address before drawing the building.For the full cost comparison, see Basement Apartment vs. Garden Suite. New to the terms? See setback, servicing and as-of-right.
The yard, not the inside.
This page is about the backyard and the structure itself. It doesn’t cover interior requirements like egress windows or fire separation, which are basement-conversion specific. See Basement ADU Requirements for that side of the comparison.
Common questions.
How big can a garden suite be in Ontario?
There’s no single Ontario limit: your municipality’s zoning by-law sets it. In Hamilton, for example, a detached unit can be up to 75 m², or the house’s floor area if that’s smaller. Check your city page or ask us for your address.
How does a garden suite get water and sewer?
New water, sanitary sewer and hydro lines run out to the suite, shown on a servicing plan submitted with the building permit. Where they connect depends on the municipality: Hamilton, for example, requires a detached unit to connect through the main house, not separately to the street.
Pick the question closest to yours.
Does my property qualify?
Zoning, parking and servicing for your address.
ADU Terms Glossary
Setback, servicing, as-of-right and the rest, defined plainly.
Basement Apartment vs. Garden Suite
Cost, timeline, zoning path and servicing, compared side by side.
We’ll walk your lot and tell you exactly.
What fits, and which zoning path applies, before you spend anything on drawings.