The rule changes by municipality
Start with the city where the property is located.
Taller or more complex walls should be reviewed before construction. Landscaping work can also intersect with grading, drainage and tree requirements.
Because location is part of the trigger, property context and site conditions must be reviewed before construction.
A wall outside that exemption should be reviewed before construction. Grading, drainage and applicable-law conditions can still matter.
Height is the key published threshold. Grading, drainage, lot lines and other approvals can still affect the project.
The Town’s grading guidance also requires retaining walls and tie-backs to remain on the subject property and addresses drainage behind the wall.
Toronto lists certain retaining walls more than 1 metre high in public or publicly accessible contexts as permit-required, while private walls that are not accessible to the public and/or are under 1 metre can be permit-exempt.
The designated-structure trigger depends on both height and location, including public property, building access and private property open to the public.
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.