Modular construction

The benefits of modular construction

Modular construction can generally be described as any form of construction where some form of prefabricated component or module is brought to site pre-assembled and erected into the final structural form.

(Above) Intelligent Building Systems International.

The intent of modular construction is to maximise high-quality off-site manufacturing and minimise on-site building activity and use of trades, hence also minimising the amount of labour on-site and its attendant workplace health and safety risks. 

In this context, structural steel has utilised prefabrication for many years. In recent years, however, modular construction has has come to be associated with the concept of ‘volumetric modular’. This describes prefabrication taken to the extent of manufacturing complete three dimensional work or living spaces off-site, which are then brought to site complete with main structure, internal finishing and all internal services complete.

These volumetric units may be stacked beside and on top of one other and connected together to form a fully functioning building. The modular units are generally self-supporting and may be able to be stacked up to multiple levels. For larger or higher structures, the imposed dead, live and environmental loads may be resisted by either a supplementary or primary structural system comprising conventional steel framing, creating a building structure that may function structurally in a hybrid manner, sharing load between the modules and additional steel framing. 

Volumetric modular unit placed onto a multi-level building. Courtesy Hickory Building Systems.

Typical module configuration

A module can be constructed from a range of different building material but, in practice, steel is the material of choice. This is particularly the case for the main structural framing and system, which can take advantage of the inherent lightness, strength, ductility and robustness of steel material and structural steel framing to withstand raking loads during transport.

There are many forms of modular systems on the market, a number of which are proprietary (typically in respect to connection details between modules). 

There are a number of different types of modules to service different functions within a completed building structure: 

  • Four-sided modules (i.e. all four sides are clad) 

  • Partially open-sided modules 

  • Open-sided (corner-supported) modules 

  • Modules supported by a primary structural frame 

  • Non-load bearing modules 

  • Special stair or lift modules 

  • Hybrid modules that may rely on other elements to resist some or all of the imposed structural actions. 

Steel's natural advantages

Modular construction capitalises on the inherent properties of steel to provide a number of key advantages relative to conventional construction: 

  • Shorter build times: of the order of 50–60% less than traditional on-site construction in some cases

  • Reduced schedule risk: from bad weather, due to reduced on-site works

  • Superior quality: due to factory-based quality control and pre-design of similar modules

  • Safer construction: due to less labour and time on site

  • Economy of scale: due to repetition of similar prefabricated units

  • Improved sustainability: due to less wastage in controlled manufacturing environments

  • Use on infill sites: modules may be used on small urban infill sites

  • Lower weight: provides lower foundation loads and expense and the ability for roof-top extensions to buildings

  • Less disruption: to neighbourhood construction sites from multiple truck movements associated with conventional onsite construction. 

Innovation in modular construction

Innovation is current and ongoing in the relatively young area of modular construction in Australia. There are a number of focus areas for innovation, including: 

  • Structural systems for both the modules themselves and also for the configuration of primary and secondary external framing systems where modules are used in larger buildings 

  • Connection systems for quick and easy coupling (and decoupling) of modules on site 

  • Configuration of service systems (plumbing, drainage, power, air-conditioning, etc.) for rapid site installation and ongoing servicing 

  • Contractual models to sensibly assign commercial risk, recognising the supply chain structure is different to conventional construction methodology. 

Modular connection systems research. Courtesy Swinburne University.

The ASI Steel Innovation Portal provides details of recent and ongoing research in this active area.


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