Irwinconsult has structurally designed the world’s tallest modular building in Darwin. At 29 levels, the recently completed Soho Apartments sets a new record.

Constructed from level seven upwards in whole-apartment prefabricated modules, this building pushes the boundaries of modular construction. Soho Apartments top at out Level 28 (29th floor above ground).

Irwinconsult developed the systems used to prefabricate the apartments and hotel suites offshore. Working closely with our client, builder/developer Gwelo, and its appointed architects, Sidecart Studios and DKJ Projects, the project incorporates 21 modular floors built on a podium. This podium structure comprises a basement and eight levels above ground with restaurants, function rooms, office, hotel reception and parking for 320 cars.

The unique challenges of a labour-constrained Darwin market led to the prefabricated modular solution.

The extreme cyclonic conditions and buyers and occupants expectation resulted in the choice of concrete floor slabs for the modules. This allows for the high humidity of a tropical climate which can prove problematic for lightweight floor solutions. The concrete floors have also simplified fire-rating and acoustic issues, particularly when combined with a partial concrete ceiling and concrete columns.

Concrete columns were poured in-situ into formwork provided by the steel columns built into the module walls. This carries the weight of the modules whilst locking them together resulting in transferring very high wind loads back to the core and reducing the fire-rating requirements of lightweight framed infill walls and ceilings. The use of concrete in the modules is unique, and resolves many of the problems encountered in typical modular construction.

The details of a typical module are shown in the images above.

This shows the module in transport mode where the stability and support for four-high stacking and two-high shipping is provided by the steel framed walls with steel column formwork, being the major load carrying elements. External cladding to walls and roofs provides a weather tight box for transport. Steel fitments are provided for lifting and for the lashing required for shipboard transport.

Overall lateral stability is provided by a conventional concrete, albeit precast, core. The solutions for the precast core elements were also unique and utilised vertical circular-column voids cast into the precast walls to allow continuity of vertical reinforcement to be achieved with simple in-situ pours. This increased speed significantly as well as reducing the weight of the precast elements for handling.

Irwinconsult provided all structural design for handling in the factory, truck mounted transport, lifting at the port, two-high ship transport, lifting on site and in-service conditions as well as detailing for fire-rating, fabrication and lightweight concrete mix design advice. We also provided Civil and Electrical design for this project.

We were involved from the inception of this as a ‘modular’ project through to the final completion in September, 2014.