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A garden suite is a detached, self-contained home in your rear yard — a backyard house, sometimes called a laneway suite where it fronts a lane. Demand jumped after Bill 23 made a third unit possible on most lots.
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A garden suite sits DETACHED in the rear yard, unlike a second unit which is carved out inside the existing house. Because it's a separate structure, its size is driven by rear-yard space, setbacks, lot coverage and height limits.
Under Bill 23's three-unit allowance, a garden suite is typically the third unit — house + internal second unit + detached garden suite.
The buildable footprint of a garden suite is set by the required rear- and side-yard setbacks, the maximum lot coverage, height and storey limits, and practical access for servicing and emergency vehicles. Mature trees and a driveable path to the unit often decide the real envelope.
SiteIQ computes the buildable rear-yard envelope for your parcel — including setbacks and tree obstructions — so you can see what actually fits.
Check whether your land is within a conservation authority's regulated area, and whether any heritage or overlay designation applies. These don't necessarily stop a garden suite, but they shape what's approvable.
Are garden suites allowed in Markham?
Detached additional units such as garden suites are broadly enabled in Ontario under Bill 23 and permitted subject to Markham's zoning standards for setbacks, coverage, height and servicing. Feasibility is lot-specific.
How big can a garden suite be?
Its size is limited by rear-yard setbacks, maximum lot coverage and height limits for your zone — not a single fixed number. SiteIQ estimates the buildable envelope for your specific parcel.
Do garden suites need extra parking?
Bill 23 removed minimum parking requirements for the additional units it enables. Confirm site-specific access and servicing with the City.
General guidance, not legal or planning advice. Rules turn on your specific lot and can change — confirm with the City of Markham, and use SiteIQ to read your parcel.