Formerly known as HMAS Platypus, Sub Base Platypus is located in North Sydney on the shores of Neutral Bay on Cammeraygal Country, home of the Cammeraygal clan of the Eora nation.

In August 2016, lahznimmo architects and ASPECT Studios were engaged by the Harbour Trust to achieve the outcomes of the Comprehensive Plan for the site. The site has previously been a gas works, a Naval Base providing torpedo maintenance facilities and ultimately as HMAS Platypus submarine base; before passing to the Harbour Trust. It had been closed to the public for more than 150 years and had undergone significant decontamination works.

The design considers the site holistically, taking into account its physical, environmental, heritage, cultural and aesthetic constraints. The general aims were to open the site for safe public access and recreation through the creation of a waterfront promenade and park; improve connections between site levels, the surrounding area and public transport; conserve and interpret the site’s rich history; adaptively reuse buildings on site for commercial and community use; and create opportunities for a complementary mix of activities to generate a sustainable return to the cost of maintaining the site.

With a rich industrial heritage spanning nearly 200 years, the bones of Platypus were already in place with numerous buildings suitable for reuse. Through adaptive reuse, the embodied energy of the existing buildings and site have been retained.

Lightweight walls divide the buildings into a range of different sized tenancies without affecting the base building structure. The tenancies can easily be adapted over time through further subdivision or amalgamation, and suit a range of commercial uses. Environmental performance of the building fabric has been improved through inclusion of insulation, and passive ventilation through cross ventilation and large ceiling fans.

The site had always been cut off from the surrounding suburbs and the wider city. At the two ends of the site, new linkages now knit the site back into its broader context; with an over-water pedestrian bridge as well as new public stairs climbing the cliff face.

Conceptually, all architectural injections into the site aim to be non-invasive and ‘touch the site lightly’, retaining both the existing industrial language and ecological ecosystems found on the site. Minor interventions to assist in the accessibility and orientation around the site such as a new lift, ‘clip-on’ cliff side walkways, stairs and bridge links are all imagined as a lightweight framed and clip-on family of forms – clearly modern, but taking their clue from the structural expressiveness of the industrial buildings.

Internally, a series of post-industrial public domain spaces have been created to improve orientation and permeability across the width of the site; which have involved the strategic removal of some built fabric. These include: Gateway Plaza off High Street, Arrival Square at the south end of the FIMA Workshop, the Razzle Dazzle Courtyard within the FIMA Workshop, the promenade and the Northern Park and playgrounds. They provide places to rest, play, meet, take in the views and provide space for temporary events.

Opportunities to interpret the site’s history are scattered throughout the site. For example, super graphics facing the new FIMA Courtyard recall the ‘Razzle Dazzle’ camouflage technique used by naval vessels to confuse prowling submarines. The industrial buildings have been repurposed for complementary commercial uses.

The project demonstrates how a collection of non-descript industrial buildings can be reimagined and activated as a modern urban precinct of mixed uses that is of benefit for both the local and regional population.