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Unilever Building Seismic Strengthening

Strengthening Petone’s Manufacturing Heritage

For close to a century, Unilever’s factory at the eastern end of Petone was a manufacturing hub in the Wellington Region. With Unilever moving their production overseas in 2015, the site’s new owner set about significant building upgrades in order to meet seismic regulations and the needs of new commercial and industrial tenants. Petone Engineering was brought in to help deliver this complex project.


  • Steel weight – 48 Tonnes
  • Over 2000 metres of 16mm Reidbar bracing
  • ½ a kilometre of threaded rod

A collaborative approach to reducing project complexity

The brick and timber building was designed and constructed in the early 1900’s. Given the lack of engineering in the original build, as well as a variety of historic strengthening works, the project had a high degree of both design and installation complexity. Upgrading this earthquake prone building, with its tight spaces, nearby tenants and NBS rating of less than 20%, required a novel and flexible approach.

Keyway Construction, the project managers for the upgrade, recognised these challenges early on in the project and so sought a collaborative approach. Early contractor involvement meant bringing the Petone Engineering team in at the beginning of the project so that they could work closely with the structural design engineers and project managers on structural steel elements.

Early Contractor Involvement

The rapid development of designs meant that Petone Engineering’s work had to be costed based on engineering drawings as they became available, rather than a complete building scope. With no competition on the overall pricing of the works, trust between project manager and Petone Engineering was hugely important part of this process.

Being able to quickly respond to any pricing questions was an important part of this trust. Petone Engineering’s ability to be transparent and provide an open set of books on the job made this possible.

The benefits of early contractor involvement were significant:

  • Streamlined design process between structural engineer and steel fabricators.
  • Early input into details and connections.
  • Provision of alternative options.
  • Designs that were physically practical and avoided clashes with existing services, steel work and timber.
  • Faster project delivery to meet tenant move in dates.

From the client

“The team at Petone Engineering have excellent communication skills. This is all built on the great operational background knowledge they have which reduces issues, their high level of technical expertise and ability to come up with solutions rather than presenting problems.” Barnie van Biljon, Project Manager, Keyway Construction.

With the steel fabrication and installation being seamless, this large structural steel project was successfully completed in 12 weeks.

Client: Keyway Construction Ltd
Location: Petone
Consultant: NZ Consulting Engineers Ltd


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Petone Engineering is a leading provider of structural steel and seismic strengthening, having delivered an impressive portfolio of projects across the lower North Island and beyond.