The Condor Tower in Perth, which transformed a disused building into a new city dwelling, has won the overall award at the WA Engineering Excellence Awards.
Constructing the innovative mixed-use building involved adding 18 storeys to the vacant 10-storey Oakleigh House in St Georges Terrace.
The project, which was carried out by engineering consultancy Pritchard Francis, is believed to be unique in Australia and possibly worldwide.
The "piggy back" construction method required custom engineering solutions that were the product of four years of research at the University of WA.
Work at the site converted an obsolete building into a new city landmark.
Because the existing concrete structure was re-used, there was reduced concrete consumption and less building waste going into landfill.
In its new structure, the Condor Tower is 100m tall and incorporates an undercroft carpark, two commercial floors and 25 residential floors that accommodate around 400 new inner-city residents.
The judges commended the project and said it demonstrated how the re-use and extension of a building could be cost competitive compared with the option of demolish and rebuild, or even result in a cost advantage, as was the case with the Condor Tower.
The WA division of Engineers Australia, which organised the awards, said the building ventured into new areas of structural design and analysis, in terms of understanding load distribution between the new and old structures and interactions between new and old concrete.
The judges said a major engineering challenge was to strengthen the existing foundation to support additional floors.