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News & opinion

4 FEB 2019

Introducing 3D volumetric, modular construction

Saviour of the housing crisis, revolutioniser of the industry, champion of sustainability: Gerard Wood MRICS and Angela Lee explain the benefits of the latest modular construction process.

Three-dimensional volumetric construction is a modern method of building by which large, often room-sized modules are manufactured in a factory, then transported to site and craned into place. The modules can also be fitted out before reaching site. The method is suited to buildings with lots of repetitive design such as houses, hotels, schools and prisons.

In its purest form, the volumetric modules slot together like a jigsaw and do not require a separate superstructure or extra facades. But the industry has yet to fully embrace the model, and projects often take a hybrid approach that combines offsite and traditional methods. For example, panels could be attached to a steel, timber or concrete frame, or a brick “skin” added to give the impression that the building has been conventionally constructed.

Construction worker
Modular construction could lead to savings in time, materials and labour

Hybrid construction is popular with contractors, but it fails to reap the full benefits of volumetric. This is because it still requires sizeable teams of tradespeople on site, as well as complex sequencing of work. Volumetric, by contrast, has the potential to bring colossal wins in time, waste reduction and quality control.

Express delivery

Buildoffsite’s 2013 report, Offsite Construction: Sustainability Characteristics, concluded that volumetric construction can cut programmes by 60%, leading to substantial savings in time-related costs such as site insurance, security, waste disposal and temporary offices. With shortened delivery times, developers can bring properties faster to the market, reducing their borrowing costs.

Claims for the environmental benefits of volumetric are many. For example, waste can be reduced by up to 80% because it is easier to work with precision in a factory-controlled environment, as well as to protect materials from damage. Logistically, as deliveries to site are reduced by up to 70%, embodied carbon can be slashed.

Keeping it tight

Consistency of process also drives up quality. Projects with volumetric modules have demonstrated 80% fewer defects and dramatically reduced snagging phases compared with traditionally constructed buildings. Occupiers also feel the benefit because the modules tend to be well insulated and more airtight. It is calculated that volumetric construction could reduce a typical building’s operational energy consumption by as much as 20%.

Projects with volumetric modules have demonstrated 80% fewer defects and dramatically reduced snagging phases compared with traditionally constructed buildings.

The size of the modules is usually limited by logistics: they are often designed to be just small enough to avoid requiring an escort when transported. However, this does not necessarily restrict the size of a completed room: modules can be joined together and internal walls removed.

At present, manufacturing often involves employing tradespeople to use traditional methods inside large sheds. However, as the sector scales up to meet predicted growth in demand, manufacturers are expected to increase investment in automation. Mass-production techniques will enable them to offer more variation in standardised designs, which could expand volumetric’s appeal into areas such as low-rise housing.

Volumetric is already shaking up industry hierarchies as manufacturers expand into site management and contractors develop manufacturing expertise. To keep pace with this change, the professions will need to rapidly acquire new skills and adopt new mindsets. For example, as BIM links up with design for manufacture and assembly (DFMA) processes, architects and engineers will need to think about the manufacturing properties of each element that they are designing from the outset.

Quantity surveyors used to working in traditional teams will find forecasting and managing costs more challenging. At present, the industry has a lot of data about in-situ construction, but less understanding or knowledge of the time and costs of offsite processes.

Cost of progress

Arguably, the fact that many people still take a traditional approach to costing volumetric projects is one reason why the sector is growing relatively slowly. At present, volumetric construction can be more expensive than traditionally-built projects, making it unviable for sectors such as social housing. But this is at odds with theories of economies of scale.

The UK has a severe housing crisis and the government is falling dramatically short of its target of building 300,000 new homes a year. Volumetric has a vital role to play in improving productivity and creating high-quality dwellings. Its time is coming.

  • Dr Gerard Wood MRICS is associate dean (academic) and Professor Angela Lee is associate dean (enterprise and engagement) at the University of Salford’s School of the Built Environment.

This article was originally published in Modus magazine (November-December 2018).