Accessory Dwelling Units in Markham - Design, Permits, Construction

Unionville and Markham Village sit inside designated heritage conservation districts, so a rear-yard garden suite there needs Heritage Permit approval on top of the building permit - cladding, roof pitch and window proportion all get reviewed. Cornell and Wismer lots two concessions away have no such requirement. Markham permits additional dwelling units city-wide, but heritage designations in Unionville and Markham Village add a Heritage Section 42 review to rear-yard construction.

Mixed - heritage-district lots with strict design review, alongside large 1990s subdivision lots in Cathedraltown and Wismer with ample rear yards. Markham sees 137 cm of snow and -4.5°C winter averages. Ontario's 1.2 m frost-depth requirement governs every footing we pour for accessory dwelling units, and the April-November season sets the excavation window.

Four physical forms are available on a Markham lot - detached garden suite or laneway house, an internal basement or upper-floor suite, a garage conversion, and a factory-built module - and the lot itself, not preference, usually decides which two are realistic. We run a feasibility overlay on the parcel first - zoning envelope, servicing capacity, rear-yard access - and only then price the two forms that survive it. Bill 23 permits up to three residential units as-of-right on most serviced Markham lots, which removes the rezoning application from the default path.