Arup homes in on prefab market
Arup has announced that it is working with architect Ken Shuttleworth to develop a system for modular prefabricated housing that can, it claims, be produced at a significantly lower cost than conventional housing.
Arup director Roger Ridsdill-Smith has been working on the project that will, he said, 'produce a process rather than a final result'. The structural engineer said that this was essential if the prefabricated units are to be made on a large enough scale to be economic and to have some impact on the housing shortage.
Speaking at the annual Lignacite lecture last week, he said: 'They must suit everybody, not just people like me.' Ridsdill-Smith's solution is a factory-produced reinforcedconcrete system, which the team has named 'Movocosy'. The essential requirements of the system are complete flexibility in the size of the units ('We don't want all of our buildings to be the approximate size of the back of a lorry, ' said Ridsdill-Smith); that the units should be stackable in many different ways; and that it should be possible to create doubleheight spaces, open rooms and clear spans without downstands.
It should also be possible to create balconies, to cantilever the units and to have an entirely clear glass face.
Stating the reasons for choosing reinforced concrete as the structural material, RidsdillSmith said: 'It is very hard to satisfy acoustic requirements without concrete floors. You can pour to fit, it is sustainable and it is low technology. We are using well-understood materials.' Ridsdill-Smith aims to use his prefabricated system to produce higher-quality, more imaginative apartment buildings at a lower cost than is currently possible.
'The only way a factory-based system can win, ' he said, 'is if the factory costs are less than the costs on site.' Ridsdill-Smith said savings could be achieved by:
l using an unskilled workforce;
l being more efficient;
l reducing efects;
l having a faster programme time; and l reducing aste.
However, this will only work if the buildings have been designed specifically for factory manufacture. The larger the proportion of the manufacture that can be done in the factory, the greater the savings will be. 'The objective, ' Ridsdill-Smith said, 'is to have high quality, low-cost homes. You can't rely on a subsidy.' He has been working with two practices: Shuttleworth of Make, who also spoke at last week's lecture, has looked at planning a block where the apartments are all angled from a central corridor; while Sophie Nguyen has been examining possible interior arrangements to demonstrate the flexibility that is possible, and the avoidance of a prefab aesthetic.
Asked how he would overcome the barrier of initial cost on the first project, Ridsdill-Smith said that the group would look at demonstration projects, which would not be factory made at first. Then, once a factory was set up, the cost would be amortised over a number of real projects.