CONSTRUCTION AS A PROCESS

A contemporary construction project typically sees materials and components that have been brought to site, where they are assembled by people – usually with the support of lifting equipment such as cranes, that are also controlled by people. This traditional model for delivering buildings is inefficient, resulting in huge wastage of materials and time. There is also a high risk of human error, and physical danger for those carrying out the work.

A significant increase in the use of digital design and off-site manufacturing is being widely posited as the solution to overcoming these problems, whereby buildings are divided into modules which are constructed in a factory and transported to site for assembly.

The concept of off-site construction is not a new one. It has long been held as a panacea for the construction industry. Prominent examples of prefabrication exist from the post-World War II, period when it was envisaged as the most effective way of rapidly rebuilding houses to address desperate shortage. However, it is interesting to note that of the 1.2 million homes built between 1945 and 1951, only 12.5% where prefabricated. The most effective solutions focused on simplicity and speed of construction.

The perception many people hold of ‘off-site manufacture’ is volumetric construction – where buildings are divided into lorry-sized blocks and transported to site, having been pre-fitted with fixtures and finishes in a factory. These units are connected together, to create a structural and functional whole. The investment required to set up manufacturing facilities that prefabricate such units, has been a key barrier. Maintaining an order book to keep these types of factories working at full capacity throughout economic peaks and troughs to see a satisfactory return on investment is difficult, especially for an unproven system.

Creating buildings using this ‘volumetric’ approach requires high levels of transportation. To give an example, The Shard in London has an approximate total volume of 330,000 cubic metres. If this were delivered volumetrically in lorry sized units of 45 cubic metres, 7,300 lorry trips would be required to deliver them to site. If we consider breaking the physical structure into component parts for assembly on site, there are around 54,000 cubic metres of concrete, requiring 1200 lorry trips to and from site. The façade includes 56,000 square metres of glazing. Packed efficiently, this would require some 124 lorry trips to deliver the external skin. This calculation indicates that onsite methods would deliver the structure and façade with approximately 75% fewer lorry trips than an offsite method.

Accordingly, the cost of shipping empty air in volumetric construction has to be at the heart of the discussion around offsite construction, what methods we might use to manufacture a modern city.

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BuildDan Cash