Prefabrication is a construction method in which large components of a structure are produced in a factory and assembled on site. The earliest examples date back almost 6,000 years, but the technique became more widely used in 20th-century construction, initially just after the Second World War, to provide temporary housing that was quick to erect. Mace, the international consultancy and construction company, completed the building of two residential towers using a radical new ‘jumping factory’–a rapid construction method involving a self-contained factory, which is housed in a giant tent built on top of the new building. Many modern construction products are produced off site, but the preassembly of larger and more complex building components is currently undergoing something of a revival. The method is credited with a 30% increase in delivery speed and a drop in the cost of risk–which constitutes a substantial part of construction costs.