A fence bylaw does not prove where the property line is
Municipal fence rules generally answer questions such as allowable height, location, materials and safety. They do not turn an assumed boundary into a surveyed boundary. If the exact line is disputed or uncertain, the fence rule and the boundary question need to be handled separately.
Use reliable boundary evidence before building on the line
Old fences, hedges, sheds and mowing patterns are not reliable substitutes for survey evidence. A current survey, real property report or other accepted land-survey information can help establish where the legal boundary is. If monuments or pins cannot be located, a qualified land surveyor may be needed.
“Line fence” does not mean the city has settled ownership
Toronto, for example, defines a line fence as a fence located on the property line between neighbouring properties. That definition helps the city apply its fence rules; it does not by itself resolve a private disagreement about the true surveyed location or who must pay for a fence.
See the City of Toronto fence guidance.
Setbacks, easements and access can still matter
Even with a known boundary, utilities, easements, drainage features, lanes and municipal rights-of-way can affect where a fence should be placed. A fence entirely inside your lot can still interfere with an easement or required access.
Neighbour agreement is useful but not a survey
Discussing the plan with the neighbour can prevent conflict over appearance, access and construction timing. But an informal agreement should not replace proper boundary evidence when the location is uncertain or the project is expensive.