Similarly to designing housing, Australia has two completely unique techniques for construction. At one end are suburban dwellings, detached or duplex, one or two storeys high. On the other hand, multi-level apartments range from three to twenty stories and higher. Both current approaches derive from mid-20th C construction techniques, and whilst incrementally improved, they don’t meet today’s needs.

In brief, most suburban houses are still timber-frame built, clad in bricks and tiles (so-called brick veneer), with only the introduction of concrete ground slabs marking a difference to post-WW2.

By contrast, and of necessity, multi-level apartments are usually built with concrete columns and floors, with infill panels, once brickwork, now in ‘autoclaved aerated concrete’ (AAC), or other lightweight materials and curtain wall glass.

There is constant criticism of both techniques, in terms of cost, time and quality – the triangle of construction value. Eschewing incremental improvements, a complete rethinking is demanded, often championing ‘modern methods of construction’ or MMC. Shorthand for factory-built, modular construction, in whole or components, commonly known as prefab.

But MMC's impact on construction techniques in Australia remains minimal. There are several reasons, including the relatively small size of our construction sector, a conservative industry resistant to change, and the difficulties deploying prefab in existing cities, especially where redevelopment of existing buildings is seen as being more sustainably desirable.

On the other hand, whilst traditional construction has its merits and is well-entrenched, it is often considered being too slow, too labour-intensive, too weather-dependent, and often poor in quality. Our regular on-site construction industry has been lucrative to date and resists resorting to the factory.

The way forward in both techniques is to adopt a hybrid construction system. Utilise the best of traditional methods in establishing the building, coming out of the ground as it were. But thereafter, construction should proceed with as many prefabricated components, in what is often called a ‘kit of parts’ approach to building.

This process is how hybrid construction works in both techniques.

Suburban housing

Big or small, all works start in traditional construction. Footings and inground services will always be site-specific. It’s slow, messy, deeply weather-dependent, and difficult to upgrade. But once that base is established, prefabricated parts are increasingly being introduced to suburban housing.

Some are already well established: factory-assembled steel truss wall and roof frames replacing site-cut stick timber. Windows and doors with far better double glazing. Large area, but lightweight, prefab sheet materials, such as ‘structural insulated panels’ (SIPs), replace heavier conventional bricks and tiles.

Even the most resistant area to MMC, traditional concrete floor slabs with services buried underneath them, unchanged since the 1960s, is now able to be made from prefabricated parts.

Sheet claddings, increasingly sophisticated, sometimes replace traditional brickwork, but a trio of factors ensures handmade brickwork endures: its longevity is sustainable, its small unit size is endlessly flexible in forms, and it has long-term customer preference.

Whole bathrooms (and sometimes kitchens) are increasingly made as ‘pods’, i.e., mini modules. Likewise, home services (connections and metres for electricity, cold water, hot water, air conditioning compressors, PV connections and batteries) can be grouped together in factory-assembled ‘service pods’, sometimes nicknamed as ‘towers of power’.

Multi-rise construction

The ground difficulties of small buildings are greatly magnified in building basements, often required for medium-density construction. Traditional site-based work is required to overcome variable site topographies, soil and rock conditions, and groundwater levels. All of which lead to poor waterproofing outcomes, for which prefabrication is rarely the answer.

However, after getting 'off the ground', multi-level buildings can follow the same techniques as suburban dwellings in adopting a ‘kit of parts’ approach. The structure can be built in precast concrete columns, walls and floor panels. Sites are gradually being weaned off cast-in-situ concrete, given the better quality control and worker safety with precast concrete.

In the era of carbon consciousness, alternatives such as steel frames or ‘cross-laminated timber’ (CLT) are increasingly promoted. However, the demands for high standards of fire and acoustic ratings require laborious site work, and ‘lifecycle assessment’ (LCA) studies often show that ‘build once’ concrete solutions mostly win out on longevity, a key sustainability issue.

The enclosing envelope is usually panelised, increasingly turning to more updated versions of the prefabricated curtain wall approach, given sophisticated glazing materials. As in houses, the key service elements of bathroom, kitchen and service pods (packaged services) are prefabricated.

Images: traditional site construction for boarding house / co-living housing on Parramatta Rd.

Construction Process and Contractors

Aside from materials and techniques, the modern construction process (of project management, subcontracting, risks and liabilities, and firms phoenixing) has likewise been heavily criticised for poor-quality outcomes, and new approaches will be discussed next week.

‘Housing Australia – Noun + Verb' is a forthcoming book by Tone Wheeler, collecting fifty years of work on philosophy, policies, projects, planning, processes and the practice of housing.

Tone Wheeler

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