Detached ADU in Richmond Hill - Design, Permits, Construction

The Oak Ridges Moraine Conservation Plan covers Richmond Hill's northern third, and on those Jefferson and Oak Ridges lots the tree-protection and grading requirements routinely cost more than the ADU's foundation. We price a moraine site and a Crosby site as two different classes of project. Richmond Hill permits additional dwelling units subject to Oak Ridges Moraine Conservation Plan constraints on the northern third of the town.

Sloped and treed lots along the moraine where site grading and tree protection drive cost more than the building itself. Richmond Hill sees 139 cm of snow and -4.6°C winter averages. Ontario's 1.2 m frost-depth requirement governs every footing we pour for detached adu, and the April-November season sets the excavation window.

A detached unit stands clear of the main house, so it carries its own foundation, its own service laterals and its own exit - the three cost centres that separate it from an interior conversion on the same Richmond Hill lot. We trench services across the yard and pour to 1.2 m before the ground closes; framing, envelope and interior finishing then run through the cold months without holding up occupancy. Detached is the highest per-square-foot form of the four, and also the only one that leaves the existing house untouched - no shared walls, no disruption to the occupants during construction.