A few weeks ago it was reported that Charter Hall had acquired a future development site at 55 King Street for $78.5 million. The site neighbours the vacant 22,000-square-metre building at 555 Collins Street which owners Fragrance Group are looking to offload following failure to receive approval for a 90-storey 300 metre residential tower on the site.

The possibility of Charter Hall acquiring the site led me to wonder what the development potential of the combined sites may be, particularly now that Planning Scheme Amendment C270 looks set to be introduced by the end of the year.

55 King Street and 555 Collins Street in their present form.

What we know so far about Amendment C270 and how it might apply to a potentially consolidated 55 King Street and 555 Collins Street site:

Introduction of a floor area ratio (FAR) of 18:1.

The maximum FAR in the central city can be exceeded if there is a demonstratable public benefit. The public benefits can take the form of public open space, office uses, public space inside the building or social housing contained within the building.

Buildings up to 80 metres in height may be constructed up to one side or rear boundary if a minimum setback of five meters is met to to all other side and rear boundaries.

By default podiums will be limited to 20 metres in height with the discretion to increase it to 40 metres to match existing streetscapes and on certain street corners.

Towers will need to be set back at least five metres from the podium edge and likewise there will be a minimum side and rear setback of five metres for proposals which include a tower measuring 80 metres or less.

For proposals which include a tower taller than 80 metres, side and rear setbacks of 6% of the overall height will be required.

No additional overshadowing of the Northbank 15 metres from the river edge between 11am and 2pm on June 22nd.

As the above diagram illustrates the combined site area of both buildings is in the general vicinity of 3,720sqm. Applying the FAR of 18:1 yields a Gross Floor Area of 66,690sqm.

This means that the site extruded to the full extent of its boundaries would hold an 18-storey tower, however based on a 20 metre podium this would actually result in a building of 22-storeys with an overall height of 84 metres.

Extruded site vs tower and podium typology.

Working on the theory that Charter Hall might seek to develop the site into a commercial office tower, let's assume the floorplates can come down in size to allow for a taller tower with better views and a floor plate in the vicinity of 2,170sqm.

This allows for an additional five floors to be added but also requires an increased setback from the western boundary so based on a 104 metre tower that equates to a 6.2 metre setback. At 104 metres, this is only 12 metres taller than the existing Enterprise House building currently occupying the site.

Increased setbacks to allow for a taller tower.

The story is very different if a residential scheme were considered for the site. A tower of 48-storeys atop the 5-storey podium would yield a project with an overall height of 164 metres and 1000 sqm floor plates which is not too dissimilar to the likes of Victoria One, Lighthouse and Empire.

Pushing the tower as far north to the site as possible also deals with the overshadowing issue to Northbank.

Comparison of residential tower to commercial tower opportunity

Based on this very brief study it would seem that we can still expect tall, thin residential towers albeit on much larger sites and employing a true tower and podium typology.

Commercial towers appear to be constrained by the requirement from tenants for larger floor plates, although this may see a shift back to smaller floor plates in order to allow developers to go taller with office buildings in the future meaning less bulk buildings with greater separation.