As the old saying goes, a verbal agreement isn’t worth the paper it’s written on.
If you are giving up a part of common property, you are pretty much allowed to impose any conditions that you wish – if they don’t agree to your conditions, they don’t get to take over common property.
You don’t want to be a dog in a manger about this but if your neighbour wants to go ahead, it would be perfectly reasonable, if not common sense, for you to ask for:
- Written guarantees about noise (especially with regard to flooring)
- Written guarantees about the future maintenance at their cost of what was previously common property
- An agreement on an adjustment to the Unit Entitlements addressing their additional holding
- Payment for the purchase of the Common Property based on the estimated increase in value of the unit, minus the cost of building it, divided by two (since you are only a two-unit scheme).
- You want all of this in a by-law written by your strata lawyer at the other neighbour’s expense.
Any reluctance to agree to any of these conditions should be enough for you to say no. It’s not about screwing an unfair advantage, it’s about protecting the value of your property and allowing the neighbour to do what they want without getting a free ride at your expense. Remember, once that common property roof space has gone, it’s not available for your use in the future.