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Last edited 03 Jul 2019
‘Factory-made housing’ refers to the process of making pre-fabricated building components (or entire housing units) in a factory. The components can then be delivered to site and assembled to create a house, parts of a house or many houses. Another term is ‘prefabricated housing’ or the now more commonly used term ‘off-site manufacture’(OSM) – which also covers other building types.
Factory-made housing involves making components off-site but very rarely the production of a complete house that is subsequently delivered to site. While this is technically feasible, particularly with small bungalows, the size and bulk of the final product involved can make transportation problematic.
However, while making complete, ready assembled houses in factories is not practised, making ready-assembled, fully-equipped modules that go to make up a house is incrasingly common. This is sometimes referred to as modular housing. Fully-fitted kitchens and bathroom modules, for example, can be made off-site ready for delivery to site. All that is typically required is fixing into place and connecting the services (e.g water, electricity, gas and drainage). The process is fast, economical, uniform, and can achieve better quality than that from a site-based operation. The Mayor of London stated that ‘...OSM buildings can be built and occupied in half the time of conventional buildings, requiring fewer vehicles to transport materials to site’.
 What is involved?
The basis of factory-made housing components is standardisation. Multiple components that are identical or very similar in size, shape and material composition are made under exacting factory conditions, unaffected by the weather and allowing greater speed and accuracy. This is why prefabrication can be more economical than making lots of different components and subsequently assembling them on site subject to the weather.
A prefabricated house will typically be of lightweight construction, have shallow foundations and can be completed faster – up to 30%-70% faster – than traditional site-based building solutions. To this should be added the reduced lorry-loads to site and lower impact on the local community, which together lead to less noise and pollution.
It is important to ensure that the overall design and the design of the individual components are correct from the outset. Whereas traditional building can make changes and amendments on site to make sub-standard elements fit together, off-site components must be exactly right, made to fine tolerances to ensure that site assembly is trouble-free.
 Benefits of off-site manufacture
- Housing can be created quickly so it provides a possible solution to help solve the housing crisis;
- Economical, both in terms of materials and labour;
- Better accuracy than on-site as components are made to exacting standards;
- Better quality;
- More environmentally friendly/more sustainable.
- Less noise, pollution, less waste, and
- Minimises disruption for local residents.
Critics of pre-fabricated housing often cite the ‘mechanical’ or drab-looking buildings that result from pre-fabrication. Also, early variants had a number of problems such as condensation, cold bridging and flimsy cladding. While this may have been the case in the early days of pre-fab housing, today there are more companies offering the service, many of which have learnt the mistakes of the early attempts of the period 1945-1975. Some of these firms are now providing a stylish, refined product that is indistinguishable from one made in the traditional site-based process.
Property developers are embracing the method to speed-up the delivery of new homes. Typical of the new genre are the houses made by Huf-Haus which sport modernist lines and do not betray their factory origins. But they can also be given a traditional look if required e.g with an external brick skin and slate tiles.
The early part of the 21st century sees modular housing providing functional homes fit for habitation as well as providing solutions for the acute housing shortage. The method is even being used for modular skyscrapers, such as the 23-storey Creekside Wharf in Deptford, London. Furthermore, the world’s largest modular housing factory was set up by Legal & General in Yorkshire and can produce 5,000 homes per year.
 Related articles on Designing Buildings Wiki
- British post war mass housing.
- BSRIA launches Offsite Construction for Building Services topic guide.
- Design for Manufacture and Assembly (DfMA).
- Kit house.
- Modular buildings.
- Offsite manufacturing.
- Off-site construction.
- Off site, on track.
- Structure relocation.
- The overlooked secret of off-site fabrication.
- Y:Cube development in Mitcham.
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