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Dunedin Law Courts, New Zealand

Sustainability through conservation

The restoration and strengthening of the Dunedin Law Courts demonstrate the Ministry of Justice’s ongoing commitment to New Zealand’s heritage and culture, reducing investment in new construction where an existing structure can be appropriately used.

The restoration work began in 2011 and the building was reopened in 2017 and well-received by the community. At the official opening ceremony, Prime Minister Jacinda Ardern said: “[The Dunedin Law Courts building] now beats with a new, strong heart and everyone involved should be immensely proud of that.”

Today, the Dunedin Law Courts building incorporates the equivalent functionality of modern courts in new buildings across Australasia. Aurecon is proud to have played such a key role in its preservation and restoration.

Reincarnation of the historic Dunedin Law Courts

In the immediate aftermath of the 2010 and 2011 Christchurch earthquake sequence, the New Zealand Government set out to reassess its public heritage buildings to determine both the potential risks and resilience of the buildings.

Prior to the earthquakes, all Dunedin court services were delivered from the Dunedin Law Courts building. Opened in 1902, it is one of the first major works to be designed by renowned New Zealand architect John Campbell.

After detailed assessment pointed to a number of potential issues, the Ministry of Justice and RDT Pacific undertook a business case to determine the future of the property. The outcome was a significant refurbishment and structural strengthening of this formerly under-utilised heritage building to bring it up to current codes and to optimise its use as a court.

Aurecon was appointed as structural engineers on the project, with an experienced project team that was familiar with the nature and challenges of working on heritage buildings and the inevitable construction challenges that go with it.

The successful completion of this restoration project has brought back to life one of New Zealand’s most significant historic buildings.

Seismic Resilience

Initial and detailed structural and geotechnical assessments pointed to a number of potential issues driven by the building’s form, construction and location on the former Dunedin foreshore.

The site slopes over a metre toward the old waterline, which resulted in a slightly uneven earthquake response. The mud and silt layers below the building were also assessed as having the potential for liquefaction, and soil weaknesses were identified under the tower.

The strengthening design was carefully conceived, with Aurecon’s structural team collaborating with heritage experts to create a solution which ensured many of the elements of the strengthening would remain hidden.

Key features of this solution included:

  • New jet grouted piles under the tower to form a more resilient base
  • Tying the masonry work together as a whole using diaphragms at each floor level and the roof level, in conjunction with fibre-reinforced polymer (FRP) tendons and sheet reinforcement
  • Concealed structural steel support of the tourelle features 

Preserving heritage aspects

The most important objectives of the project were to improve the building’s structural integrity, while maintaining its heritage aspects and its ongoing use.

Each of the structural solutions was carefully placed so their effects on the heritage aspects of the building were minimised. All key decisions made on the project were informed by a detailed conservation plan, with the building’s interior spaces, exterior and fabric thoroughly assessed in terms of historic significance.

A detailed inspection of the exterior stonework was made by the conservation architect and the stonemason. Although the building’s exterior had been recently rehabilitated, the inspection revealed a number of issues that required attention in order to minimise maintenance in the immediate short to medium term.

The project team worked with a number of specialist craftspeople in order to establish a repair methodology that could be carried out using the skills of Dunedin locals.

Architectural innovation

The project team worked closely with the architect to develop an in-depth understanding of the original materials and processes used on the building’s facade. The team employed several modern methodologies in the restoration of the stonework to delay the ageing process and therefore minimise ongoing maintenance costs.

The seismic strengthening design incorporated the innovative use of modern materials like FRP sheet and anchors, as well as traditional materials such as reinforced concrete, structural steel and timber.

Continuing the innovative design thinking, the Dunedin Law Courts building also became the first building in New Zealand to use a StoSilent acoustic plaster ceiling from Europe.

The Dunedin Law Courts won Best in Category and Excellence award (Heritage and Adaptive Reuses category) at the 2018 New Zealand Property Council Awards.

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