twinks – the only way to definitively ascertain the boundaries of the common property and of Lots within a Strata Scheme is to examine a copy of its Registered Strata Plan, where the boundaries of the Common Property are shown as thick black lines on the floor plan.
If neither your Owners Corporation (Secretary) nor your Strata Manager has a copy, then you can purchase one from the on-line shop operated by NSW Land & Property Information (incorporating the former Land Titles Office), whose staff are usually very helpful if the information that you’re after is not obvious from your examination of the Plan.