The rule changes by municipality
Start with the city where the property is located.
The City’s accessory-structure page is useful before purchase because it sets zoning limits such as maximum individual area, combined accessory-structure area and minimum setbacks.
Burlington’s listed house-accessory exemption applies only when the structure stays below the stated thresholds. Zoning still applies even when a building permit is not required.
The 15 m² rule is specific to qualifying residential accessory structures. Other uses can have a 10 m² threshold, and zoning still applies.
Kitchener’s shed exemption is conditional. The proposed use and services matter, not just floor area.
A shed outside any of those conditions requires permit review, and zoning still applies.
Markham’s current permit-process page lists the under-15 m² accessory-building exemption for housing projects. The structure still needs to comply with the zoning by-law.
Mississauga lists a shed less than 15 m² as permit-exempt when it is one storey, free-standing, used for storage only and has no plumbing. Accessory-structure zoning rules can still regulate location, size, height and lot coverage.
All of these structures still need to comply with the zoning by-law. The Town recommends verifying the proposed dimensions and location before preparing the permit application.
The City also publishes a shed and garage construction guide for residential applicants.
Ottawa distinguishes qualifying one-storey storage sheds from other accessory buildings. Zoning requirements such as setbacks, building height and lot coverage can still apply even when no building permit is needed.
The easy mistake is treating “no building permit” as “build anywhere.” Permit thresholds and zoning rules are separate checks.
Vaughan publishes a specific shed exemption but distinguishes it from other accessory structures. Zoning and, in some projects, separate engineering or grading requirements can still apply.
Waterloo distinguishes the shed threshold from the detached-garage threshold, so project type matters.
Whitby also publishes accessory-structure rules for side/rear yard placement, height and minimum lot-line setbacks.
Ontario sets the Building Code. Municipal rules, zoning, processes and project guidance still differ.
We publish a city only after attaching municipal sources to the project answer. Missing coverage stays missing instead of borrowing another city’s rule.