Expert opinion

An insider’s guide to prefab housing

We have plenty of group and volume house builders, but what can we do to switch them onto well-designed density, instead of sprawling single-family developments on the city fringes? Group-home building companies have a sweet spot in suburban subdivisions of separate houses, dabbling in multi-unit housing, using prefabricated building components. But repetition of buildings are not well received by their clients, who prefer some individuality. A major issue is dealing with mass customisation: individualised design with efficiencies from repetition. Group builders are not great at dealing with medium and high density, they too often minimise or cut design from a project. Design needs to lead these projects. There are plenty of small manufacturers of components. What is needed to ramp them up to produce volume, quickly? The prefab industry is disrupting the ways we build but it’s incremental innovation – small shifts of prefabricated elements within conventional building, for example wall elements. They may include new systems that use BIM (Building Information Modelling) and file-todigital fabrication to automate design, construction and delivery of buildings. The big issue is standardisation, then? New Zealand’s housing market has historically been too small to sustain prefab manufacturing growth. Architect-initiated, purpose-designed buildings may not incorporate construction system knowledge and if design is not informed by that detail, there are big compromises made to adapt it for a system and redesign at the developed design phase. We need to help small and medium businesses work together to adopt common construction and prefabrication protocols, get dimensional coordination between different systems but still retain competitive tendering between suppliers. Right now we rely on developers to create new housing, what other ways of building are there that could help strip out costs? The false idea that the market will deliver affordability is the problem. As any builder will tell you, at a certain point cheap is counterproductive in terms of long-term performance. Unless the government finds a way to manufacture housing ourselves, like it did historically with the railway houses, then the cost of housing will be whatever the developer can sell it to the market for. Direct collective building procurement with net-cost building (like cohousing, Baugruppen, and Australia’s Nightingale) are emerging here, and groups are connecting through social networking. Eventually the sustainability will be recognised by government. How can the government deliver on its 100,000 homes promise? A very effective historical precedent in Vienna in 1923 created 25,000 housing units in five years, and 60,000 in 10 years, using more than 190 architects. We have a building industry of small-tomedium architects and builders that, together, are a huge collective resource. If they all gear up a little, it can happen quickly. Imagine the progress if 100 architects and 100 building teams were directly engaged in parallel to provide high numbers of medium-density, affordable housing projects in the same time frame as a single building project? It is much more productive to use many small, lean administrative structures, as opposed to a few big, high-overhead greedy ones.