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Steel at Heart of Good Buildings

(originally published 16 March 2016)

20 Martin Place was set to be demolished when a project team created a new and sustainable vision for it. The ambitious project culminated in the delivery of a 6 Star Green Star office building that reused its original steel frame structure, a reuse that is even greener than recycling.

The expectations of occupiers have shifted dramatically in the last two decades. 

In modern office buildings, sustainability credentials are a high priority. Moreover, modern design demands not only an impressive exterior, but greener workspaces, flexible floor plates, up-to-date building systems and technology and interconnectivity. 

When Pembroke Real Estate purchased 20 Martin Place in 2011, it was clear that, despite its prime location in the Sydney CBD’s retail and business precinct, the building was outdated and in need of major refurbishment. In fact, it was headed for demolition, according to Matthew Knight, development director of Charter Hall, the development manager for the redevelopment of the property. 

However, in a unique twist, planning controls around building heights led the project team behind the redevelopment to retain the original steel structure of the building, which dates back to 1974.

“New planning controls have reduced the height of new development to 55m [and] with the existing building exceeding this height, it was essential to retain the existing steel structure to maintain the height of the building,” explains Greg Crone, CEO of the project’s architecture firm, CRONE.

The new 20 Martin Place was to achieve the maximum FSR (floor space ratio) allowed by the City of Sydney, without increasing the height of the building.

The brief evolved: a project team would deliver a completely new building, provide a 25 per cent increase in net lettable area, whilst building off the existing steel frame.

It was a situation that had its benefits for design and sustainability.

The architects at CRONE, who worked on the design in association with James Carpenter Design Associates in New York City, relocated the new structural core to the northern edge to deliver an improved typical floor plate design.

“Being a steel frame structure the core provided flexibility to relocate the core from within the existing building envelope and reconstruct the new core attached to the north façade,” said Crone.

Repositioning the core would allow for an increase in the amount of usable floor area and the efficiency of the floor layout without breaching the building’s constraints, which Crone said would increase flexibility for fit-out.

The project itself, he adds, proved an insightful experience.

“Retaining existing structure can be a viable alternative to demolition particularly where steel framed structure is involved,” he said.

Built on sustainability

20 Martin Place was awarded a 6 Star Green Star – Office As Built v3 certified rating, and the owner, Pembroke Real Estate, says that it’s “set to receive a 5 Star NABERS certification” through its high performance glass façade, water conservation measures, upgraded plant equipment, lighting controls and the greening of lower level roof terraces.

Crone acknowledges the sustainability benefits of retaining the existing structure. More specifically, adapting the existing steel frame helped to achieve a Green Star Rating from the Green Building Council of Australia, with points accrued through the ‘Building Reuse’ criteria.

Built on steel

Liberty OneSteel, which supplied the steel for the original frame in the 1970s, detailed the development process in ‘20 Martin Place, Sydney CBD: Innovation sees old transformed into new’, including the removal of the former façade, floor slabs and non-structural core.

Liberty OneSteel also considered the process behind the retention of the steel frame, noting that the work of structural engineers Taylor Thomson Whitting in assessing the “structural adequacy of the structural steel frame during the construction phase”.

With the original core relocated, new floor areas were created, Wystan Alexander, Associate at Taylor Thomson Whitting told Liberty OneSteel, with the floor plate extended 3.5m on the northern edge of the new core to the northern perimeter precast wall.

“The framing for the new floor areas incorporates composite structural steel beams, supporting a concrete slab on metal decking.”

The redevelopment required the installation of only one new column, with most of the new steel beams being supported off the existing steel frame or the new concrete core.

“Structural design of the floor beams was done using the Liberty OneSteel software CompPanel, which checks both the strength and serviceability criteria of the composite beams,” said Alexander.

A new life

The 19,000sqm building has a high-performance shingled glass façade that reflects the sun’s movement throughout the day.

Located in the heart of Sydney CBD’s retail precinct, the $100m development has three levels of retail and houses several tenants, including a new flagship branch of ANZ and an anchor tenant that is yet to be announced. 

Project stakeholders

Crone Partners Architects in association with James Carpenter Design Associates, NYC


Pembroke Real Estate

Development Manager 
Charter Hall

Project Manager              

Structural Engineer 
Taylor Thomson Whitting

Services Engineer            
Aurecon (Initial Design)

Electrical Engineer          
Norman Disney & Young (Initial Design)

Planning Consultant       
JBA Planning

Quantity Surveyor