There are a few concerns with this. Firstly, they shouldn’t be making decisions about common property without special resolutions, including who will have responsibility for the structures when the work has been done. The significant change in the construction is, I believe, a valid reason to demand another vote.
Secondly, is this owner taking part of common property to enhance the value of their own lot? If so, have they paid the owners corporation the required compensation (the amount by which the value of the lot has been enhanced minus the cost of construction).
Finally, NCAT is supposed to be a low-cost (no lawyer) avenue for resolving disagreements and owners have to seek permission to have lawyers represent them.
You could put forward a case that this is a simple issue of them not following strata law and that being forced to have a lawyer representing you is a cost that you shouldn’t have to bear as you are the ones just trying to have the law enforced, so they shouldn’t have one either.
Or you could go for a low-cost option like our sponsors Strata Answers.
You can complain about strata managers to Fair Trading HERE.