New Zealand Commercial Design Trends Series NZ Commercial Design Trends Vol. 33/03C | Page 62

light to the centre of the large floor plates, as well
as the Banking Chamber, had been infilled. We
designed a contemporary glazed atrium with a
glass floor over the reconstructed lay-light,
interpreting and referencing the extensive original
decorative glass elements throughout the building
and transforming both the commercial floors and
the former Banking Chamber.”
A key part of the restoration was setting the
co-ordinated services within an integrated chilled
beam unit, sweeping out the clutter of concealed
services hidden by false ceilings and allowing the
existing heritage ceilings to be exposed.
The Banking Chamber and other protected
spaces have since been retrofitted for retail, with
the heritage elements remaining in full prominence.
Cbus Property’s and Dexus’ aspirations for the
project showed their recognition that the building’s
heritage values are integral with its commercial
value. This was seen in the joint-developers’ willing-
ness to sacrifice floor space for the re-introduction
of the building atrium; their commitment to reveal-
ing and repairing the 1916/33 spaces, elements
and finishes and, lastly, to commit to the extreme
structural complexity of the cantilevered tower so
that the existin g building was not compromised.
Redevelopment of the 1960s addition and the
creation of the new office tower was generally the
responsibility of JPW.
“We reworked the 1960s element with a new
facade which is consistent with and articulates the
height, scale, design concept and elegant proportions
of the adjoining 1916 building,” says Blome. “Its
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detailing also acknowledges the prominence of this
principal façade fronting Martin Place.”
The facade materials, including sandstone and
reclaimed trachyte from the 1968 building, are
harmonious with the original 1916 facade.
However, the most dramatic part of the complex
revitalising programme is the new build component
with its dramatic physics-defying structure.
The new tower rises twenty storeys alongside the
heritage building, with the upper ten floors also
cantilevering right over the historic bank building
without imposing any permanent loads on the
existing structure. The bottom half of the tower is in
concrete while the top half has a steel structure.
Aurecon was structural engineer on the project and
the company’s design director Tony Lavorato says
it involved a complex feat of engineering.
“The solution was a cantilever structure where
the overhanging structures above the existing 10th
level of the heritage building are supported using
hanging columns on the western facade, forming
an inverted king post truss,” says Lavorato. “This
delivers the load of this section of the building to
the northern and southern elevations, which rely
on a strut-and-tie arrangement to transfer the load
from the hanging columns to the main building
concrete cores and down to the foundations.”
This construction method required the tempo-
rary support of the building during construction of
the main structure and some levels of the fit-out.
This was achieved by temporarily supporting the
structure on hydraulic jacks located over selected
strengthened columns of the heritage building.
Below:Up and over – Aurecon’s
dramatic engineering for the
tower is laid bare in this graphic.
Facing page:The upper floors
of the new tower suspended
over the heritage building. The
re-established atrium admits
light right down from the heart
of the tower cantilever and onto
the reconstructed laylight ceiling
of the 1916 Banking Chamber
directly beneath it.