Fees for exclusive use of common property

Hi, I know this topic has been discussed before, but I’d appreciate hearing from others on their experience of calculating fees for exclusive use.  By way of background, I own 1 of 9 units in a 1930s apartment block.  The subject of attic conversions, exclusive use gardens, converting voids to storage or living spaces etc has been discussed for quite some time without much urgency.   However now the building requires major maintenance and repairs, and granting people exclusive use over common property and using the resulting fees to fund a large proportion of the works is gaining majority support.

However, some owners wish to apply a common formula for calculating the fee payable by each owner, and this is where we’ve hit a speedbump.  I am aware of the formula from case law mentioned elsewhere (simply put – increase in value less increase in costs to realise) but strictly applied it creates a large fee disparity that not everyone is comfortable with.  To explain more clearly, by way of example:

If owner A on the top floor expands into their attic space creating 2 rooms at a cost of $180,000 and the increased in value is estimated at $200,ooo the fee would be $20,000.

If owner B on the ground floor realises the use of some garden space at a cost of $10,000 (for access door, fence, paving etc) but the increase in value is calculated at $120,000 by a valuer, they would be asked to pay $110,000.

This disparity seems unreasonable, and of course, owner B doesn’t want to pay that much (and neither would I!).  You could argue owner A gains more amenity from the internal space than owner B gains from external space, but at less than a fifth of the cost.

There is also the issue of what constitutes a ‘reasonable’ cost of construction (as this could be manipulated to reduce the fee to almost nothing).  If other owners insist on a formal valuation, is that commonly done by the owners corporation or the individual?  Again, subject to some manipulation.

Has anyone has a similar experience and successfully resolved it?  Personally I (as a top floor owner) am happy to avoid this headache, let market forces prevail and for each of us to negotiate are own ‘fair’ deal, but its proving hard for some to get their heads around (understandably).

Any thoughts or experiences, greatly appreciated.