Free tool · Ontario · ~4 minutes
Can you build a second home in your backyard?
Garden suite, laneway suite, in-law suite, backyard rental — Ontario calls these ADUs (additional dwelling units). The rules are buried in municipal by-laws and change block to block. Enter your address and get a straight, property-specific answer: what your zoning allows, how big you can go, and which grants you might qualify for.
How it works
What the ADU Checker actually checks.
Enter your address and the Checker reads your municipality's published zoning by-law for your property, then tells you in plain language whether a detached ADU is permitted and roughly how big.
- Whether your zone permits an additional dwelling unit
- Maximum floor area and building height
- Setbacks and separation from your main house
- Lot-coverage limits
- Servicing — municipal water/sewer vs. well/septic
- Protected designations — Greenbelt, Oak Ridges Moraine, conservation overlays
- Which General Coach ADU models fit your size envelope
- Government grants and rebates you may qualify for
What it isn't: a building permit, a zoning determination, or legal advice. It's a preliminary zoning indication built from your municipality's published by-laws — confirm final eligibility with your municipality's planning department or a qualified professional.
Common questions
Ontario ADUs — your questions, answered.
What is an ADU (additional dwelling unit) in Ontario?
An additional dwelling unit (ADU) is a second self-contained home on a property that already has a house — with its own kitchen, bathroom, and entrance. In Ontario you’ll also hear them called garden suites, laneway suites, secondary suites, in-law suites, or coach houses. A detached unit in the back yard is what most homeowners mean by a “garden suite.”
Can I build a garden suite or laneway suite on my property?
Often, yes. Ontario now lets most residential lots add additional dwelling units as-of-right, but whether a detached garden or laneway suite fits your specific lot depends on your municipality’s zoning — lot size, setbacks, height, lot coverage, and servicing. The ADU Checker reads your municipality’s by-law against your address and gives you a plain-language answer.
How many additional units can I have on my lot?
Most residential lots in Ontario allow up to three dwelling units as-of-right — your main home plus two more (for example, a basement suite plus a detached garden suite) — under the More Homes Built Faster Act (Bill 23) and O.Reg 462/24. Your municipality’s by-law sets the size, height, and siting for each.
How big can an ADU be in Ontario?
It varies by municipality, but the province sets floors municipalities can’t go below: a detached ADU may be at least 4.5 m tall (one storey) or 6.0 m (two storeys), and accessory buildings can cover up to 45% of the rear yard in urban areas. Many municipalities also cap floor area — Toronto, for example, around 60 m². The Checker shows the size your municipality allows and which models fit.
Do I need a permit to build an ADU?
Yes — a building permit, and sometimes other approvals (such as a conservation-authority sign-off near ravines or shorelines). The ADU Checker tells you whether your zoning permits an ADU; the building permit itself is a separate step handled by your municipality. The tool shows you that honest next step.
Are there grants for building an ADU in Ontario?
There may be. Federal, provincial, and municipal programs — forgivable loans, low-interest loans, development-charge waivers, and rebates — can apply to building or renting an ADU. Amounts and eligibility depend on your municipality and the program’s terms, and some programs open and close. On an eligible result, the Checker flags the programs worth looking into for your area.
Is parking required for an ADU?
Generally no. Under O.Reg 299/19, municipalities cannot require parking for an additional residential unit unless a transit-distance test applies — which removes one of the most common obstacles to a backyard suite.
What’s the difference between a garden suite and a laneway suite?
Both are detached ADUs. A garden suite sits in your rear yard and is the more common option. A laneway suite is only possible if your lot backs onto a public lane — the lane provides fire-truck access, which removes the most common rear-yard constraint. The Checker accounts for both where your municipality allows them.
Which municipalities does the ADU Checker cover?
27 Ontario municipalities so far — across the GTA, Simcoe County, cottage country, southwestern Ontario (including Hamilton and Brantford), and the Ottawa–Kingston corridor — each with its own zoning rules and a last-verified date. If your municipality isn’t covered yet, the Checker tells you and connects you with a person.
Is the ADU Checker free?
Yes — it’s free, takes about four minutes, and doesn’t require an account. Enter your address, answer a couple of questions about your lot, and get a property-specific result.
Does the Checker tell me I’m approved to build?
No. It’s a plain-language read on what your municipality’s zoning permits — not a building permit, a guarantee of approval, or legal advice. It tells you where you stand and the real next step; your municipality confirms final eligibility at the permit stage.
Authorship & accuracy
Why you can trust this answer.
Built and maintained by Modular Homes 400 — Ontario's modular-housing authority. Reviewed by James Clarke, REALTOR® (TRREB) and General Manager, who has spent 40 years in Ontario housing helping buyers and landowners get factory-built homes onto real lots.
The Checker is built on Ontario's provincial ADU framework and each municipality's published zoning by-law. Provincial rules are current as of 2026, and your result shows the specific by-law reference for your municipality plus its last-verified date — so you can see exactly how fresh the answer is.