The Apartment Construction Cost Demonstration Project was an innovative and collaborative partnership between Renewal SA and the private development sector to investigate contemporary design and construction approaches to minimise building costs.

Following a public expression of interest process run by Renewal SA in mid-2014, multiaward-winning firm Mossop Construction + Interiors was appointed as the builder partner and leading Adelaide architectural firm Studio Nine was chosen as the design team leader.

 Consistent with State Government urban planning policy, identifying more cost effective construction methodologies for multi-storey residential buildings supports higher urban density and urban infill within the middle ring suburbs.

Industry and Renewal SA experience shows that typical apartment construction rates make it challenging to recover construction costs from the selling prices supported by the market outside of the CBD, near CBD locations, beachfront and other selected high amenity nodes within metropolitan Adelaide. Typical apartment construction rates are often more than double the cost per square metre of a two-storey detached home. Analysis by Renewal SA indicated that a total project construction cost between $1800 and $2000 per m² (GST inclusive) would need to be achieved to ensure commercially viable apartment developments of four storeys. This became the target construction cost range for the project which compares favourably to historical apartment build costs between $2400 and more than $3000 per m² (GST inclusive).

The demonstration project highlights the exciting potential for cost savings and improved design outcomes through early and ongoing collaboration between the design team and the builder. The preferred construction system determined by the project team was a combination of an insulated concrete form (ICF) product for the external and internal walls and a pre-cast concrete floor cassette system for the floors. The system achieved the target cost per square metre rate, with a market-tested price of $1974 per m2 (GST inclusive) or $1795 per m2 (GST exclusive) for the demonstration project. It is important to note that depending on market conditions and supplier relationships, pricing can vary. Indeed, the project revealed a plethora of new materials and emerging systems continually coming to market. Ultimately, the most cost effective system will depend on the developer’s specific apartment design.

Based on the project team’s experience, adopting some or all of the following principles were found to be effective in reducing construction costs for the demonstration project:

• Modular layout with straight and aligned walls on a grid pattern at span widths of the structural/ flooring systems
• Reducing the volume of material by designing all load-bearing walls to the ground (using direct load paths) to avoid secondary framing
• Co-location of services to allow floors to be easily ‘stacked’
• Optimal spans of around three metres to allow a wider choice of materials and to reduce waste during construction
• Designing all bedrooms, kitchens and bathrooms to be of similar size and layout to maximise replication and reduce costs
• Rationalise room orientation to have direct light and ventilation
• Easy fire compartmentalisation
• Compact common areas (which will also reduce community corporation costs)
• Moving wet areas to external walls of apartments to minimise noise-reduction costs
• Reduced building footprint
• No roof plant
• Prefabrication such as bathroom pods, pre-built internal and external walls, and floors.

Summing up: this report does not propose a single solution to every building cost challenge. Rather, it demonstrates a logical step-by-step process whereby developers can assess options in terms of design, material selection, construction methodology, site influences and building layout. The methodology outlined in this report can be applied to the construction of any multistorey apartment building.