Garden Suite Rules in Vaughan, Markham & Richmond Hill (2026)

Here's the short version. Since Bill 23 — Ontario's More Homes Built Faster Act, 2022 — up to three residential units are permitted as-of-right on most serviced residential lots province-wide: the main house plus up to two additional units, one of which can be a detached garden suite in the backyard. Those additional units are also exempt from development charges, a saving that typically runs to tens of thousands of dollars.

What the province did not do is write the fine print. Vaughan, Markham, and Richmond Hill each implement garden suites through their own zoning bylaws — setbacks, maximum height and footprint, lot coverage, separation from the main house, parking, and tree protection all vary by city and have been amended more than once since 2022. Never plan from a neighbour's project two municipalities over; confirm the current bylaw with your city's planning desk before you spend on design.

The budget frame is the same everywhere in the GTA, though: garden suites run roughly $400–$650 per square foot as of 2026, with most complete builds landing between $275,000 and $550,000 and compact suites starting around $180,000. Full details in our garden suite builder's guide for Ontario.

Vaughan is our home base — our shop is at 7700 Keele St — and it's an unusual garden-suite market because the city grew so late. Vaughan's population was static until trunk-sewer service arrived in the late 1970s; Woodbridge and Thornhill's Vaughan side filled in through the 1980s and 90s, Maple and Sonoma Heights through the 1990s and early 2000s, and the Kleinburg-area estates mostly in the 2010s.

That history shapes what fits. The older village cores — old Woodbridge, the oldest Thornhill streets — carry the mature, deeper lots where a detached suite sits comfortably. Much of the rest of Vaughan is newer subdivision fabric where rear yards are tighter and the question becomes millimetre math: can you meet the setbacks and still get a usable footprint, and can equipment even reach the backyard between houses?

Vaughan regulates suites through its comprehensive zoning bylaw, and the specifics have evolved since Bill 23 — treat any setback or height number you read online as provisional until the city confirms it. The practical first step is the same one we use: check whether your backyard can actually fit a garden suite before anything else.

Markham's stock splits three ways, and each way reads differently for suites. Thornhill's Markham side built up in the 1960s and 70s, so it has generous suburban lots — plus the era's renovation caveats, like aluminum wiring, in the main house. The historic cores of Unionville Main Street and Markham Village offer deep character lots but come with heritage considerations that add a layer to approvals. The 2000s-and-newer communities — Berczy, Cornell, Greensborough, Cathedraltown — are compact by design; Cornell's new-urbanist blocks with rear lanes are an interesting case, but small yards mean small suites, and cost per square foot rises as size falls.

Richmond Hill runs on a similar gradient: older, deeper lots around Mill Pond and the downtown core; 1960s-to-90s subdivisions through the centre and south; Oak Ridges and Jefferson from the 2000s onward. One extra flag for Richmond Hill and north Markham: properties near valleys, steep slopes, wetlands, and watercourses can fall under conservation authority regulation, which since 2024 runs province-wide under O. Reg. 41/24 — a regulated lot needs the conservation authority's permission before you build, on top of the municipal permit.

Both cities apply their own minimums, and our minimum lot size guide for GTA garden suites explains the dimensions that matter most.

The line item that surprises York Region homeowners most isn't the structure — it's getting water, sanitary, and hydro to a building at the back of the property. Suburban lots cut both ways here. The good news: those deep 1960s–80s lots in Thornhill, old Woodbridge, and Mill Pond have room for the suite. The catch: the deeper the lot, the longer the trench from the house or the street, and trenching, connections, and utility coordination are a meaningful share of every garden-suite budget.

Across the GTA, soft costs — surveys, engineering drawings, arborist reports, permit fees, and utility connections — typically add $25,000–$70,000 before construction starts. Servicing strategy is a genuine design decision: whether the suite ties into the house's services or runs new connections affects cost, capacity, and even where the suite can sit on the lot. We walk through the options in garden suite servicing: water, sewer, and hydro.

One more suburban reality: winter. Trenching and foundation work fight frozen ground, so servicing scheduled for late fall has a way of sliding to spring. Build the season into the plan, not just the budget.

The design controls across the GTA follow a recognizable template — Toronto permitted garden suites citywide in February 2022, and its framework of rear-yard placement, height limits tied to setback distance, angular planes, and tree protection set the pattern most municipalities work from. York Region's cities apply their own versions, but the intent is consistent everywhere.

• Height and angular planes protect neighbours' sunlight and privacy — the further the suite sits from lot lines, the taller it can generally be, which is why two-storey suites need bigger yards.
• Tree protection is a first-week question, not a last-week one: protected trees near the build zone typically trigger an arborist report and can reshape or sink a design.
• Soft landscaping and separation minimums keep the backyard a yard — expect required green space and a minimum gap between house and suite.

The exact numbers differ between Vaughan, Markham, and Richmond Hill and get amended, so we design to the current bylaw and confirm at pre-consultation rather than quoting figures that may be stale by the time you apply. What doesn't change: a design that respects the neighbours' light and the mature trees approves faster everywhere.

Honestly: none of the three is categorically "easiest" anymore. Bill 23 flattened the big differences — a garden suite is a permitted use on most serviced lots in all three cities, and development charges are off the table for additional units province-wide. What decides your project now is your lot: depth, tree cover, side-yard access for equipment, servicing distance, and whether a conservation authority has a claim on the land.

So the sequence we recommend is city-agnostic. Pull your survey. Book a pre-consultation with your municipality's planning staff — it's the cheapest reality check available. Get a feasibility opinion on servicing and trees before commissioning full drawings. Then budget from the real numbers: $400–$650 per square foot, $275,000–$550,000 for most complete builds, with our compact builds starting around $180,000 — the full breakdown lives in the garden suite cost guide.

We design and build garden suites across York Region from our Vaughan headquarters, and we run the feasibility step before anyone signs a construction contract. If you want a straight answer on whether your backyard works — in Vaughan's zoning, Markham's, or Richmond Hill's — a free quote and feasibility review is the place to start.