Boundaries of lots are ascertained by looking at the Plan of Subdivision. Unfortunately, the precise location of boundaries is not always clear to the untrained eye.
In addition to the Plan of Subdivision, legislative provisions are relevant. For example, Reg 10(4)(a) of the Subdivision (Registrar’s Requirements) Regulations 2011 which commenced on 8 October 2011 may apply where buildings are used to define boundaries; or for strata or cluster subdivisions, schedule 2 to the Subdivision Act 1988 may be applicable.
The difficulty is that the various legislative provisions do not operate retrospectively so the relevant statutory provisions are those in force at the time the plan of subdivision was registered.
Owners Corporation PS508732B v Fisher  VCAT 1358 examined the question of who owns parts of an exterior balcony, and therefore who is liable to maintain them. Regulation 10(4)(a) of the Subdivision (Registrar’s Requirements) Regulations 2011 and its predecessor were examined in relation to the meaning of “interior face” where buildings are used to define boundaries.
The question of the exact location of the lot boundaries is a complex one and a licensed surveyor is best placed to answer your questions. However, in some instances where there is dispute about the exact location of a boundary, the question may only be able to be resolved with certainty through the Tribunal.