What kind of project needs a full zoning bylaw amendment instead of just a minor variance in Ontario?

The dividing line generally comes down to scale and nature of the change being sought. A minor variance is meant for a narrow deviation from a specific numeric or technical requirement in an otherwise applicable zoning bylaw, where the underlying permitted use itself isn't changing, such as a modest reduction in a setback or a small increase in permitted height. A full zoning bylaw amendment, sometimes called a rezoning, is needed where the project seeks to change what's actually permitted on the land, such as introducing a use the current zoning doesn't allow at all, or where the requested deviation is significant enough that it can't fairly be characterized as minor.

Because "minor" is judged against the specific site and its context rather than a fixed numeric threshold, a project on the borderline between the two categories can sometimes go either way depending on how it's framed and presented, and a committee of adjustment can generally refuse to grant a variance it considers too significant, effectively pushing the applicant toward the rezoning process instead. Getting a professional planning opinion early on which process actually fits your project avoids wasted time pursuing the wrong application.