Homes to go

Using modular production techniques, housing units can be factory-made for rapid assembly on site. As Judith Cruickshank reports, the result is high-quality housing at a low cost

Factory-made housing: it sounds like the product of a totalitarian state where every aspect of life is regulated. But it would be wrong to think that. Modular housing can provide homes built to high standards and, if the volume is there, at a relatively low cost.

`The future of the building industry depends on clients thinking production, not construction,’ says Keith Blanshard, director of Portakabin subsidiary Yorkon. `We don’t buy our cars as components so why should buildings be any different?’

Murray Grove, a housing development in east London which Yorkon is fitting out for the Peabody Trust, should go a long way to change people’s perceptions about the style and quality of modular housing. It consists of 30 one- and two-bedroom flats, designed by architect Cartwright Pickard Associates for the Peabody Trust. Although aimed at low-income families, the flats have been fitted out to a high standard at Yorkon’s factory at Huntingdon, just outside York.

Yorkon has been in business since 1980 producing steel-framed modular buildings for offices, classrooms, hospitals and other applications. Hotel accommodation has made up a large part of its recent output. It also provides buildings for McDonald’s, and is working on a system for nursery schools.

This broad range of experience brought Yorkon into contact with Cartwright Pickard two years ago. Both were interested in applying new technology to housebuilding. When living in Sweden, James Pickard saw the high quality and technical sophistication of houses made from volumetric and flat-pack timber systems. Murray Grove is the first chance to put their ideas to the test.

Yorkon produced the scheme’s 74 modules – each measuring 8m by 3.2m – at its Huntingdon headquarters. The modules contain one habitable room (bedroom or living room) and adjacent utility space. Bedrooms and living rooms have sliding glass doors opening on to a terrace overlooking a private garden.

One-bedroom flats are made up of two modules, two-bedroom units of three modules, with a decent sized dining area included in the kitchen space. The dimensions were picked to suit the site: Yorkon can make modules up to 14m long.

The modules are a steel monocoque construction, heavily insulated to standards better than building regulations require and capable of being stacked up to five storeys high.

The module’s weight is taken by steel posts at the corners, each with a lug acting as a locator for the module placed above it. Air gaps around each module give a high standard of sound insulation – a feature Yorkon developed for hotels and further improved on for this project.

Most of the steel for the modules is cut and bent in-house, and very few components are bought in. The room modules are made on a dedicated production line with parts such as wall panels being produced on a separate line and brought in as needed. All the panels are made in jigs, and all jigs and components are checked against a standard measure.

Construction of the room modules starts with welding the cross beams to side frames to provide the skeleton of the floor section. They leave this stage as a thick steel and rockwool insulation sandwich topped with blockboard to form the floor. Electric cable is installed under the floor, accessed via circular sections cut in the board.

Wall assemblies, made of layers of plasterboard, injected insulation, steel skin and air gaps, are brought on to the assembly line and fixed. The windows and patio doors are installed in precut openings. The ceiling is added and the heavily insulated steel box is ready to be moved outside for internal fitting out.

It takes less than a day to assemble a complete module, and as much work as is practically possible is done at this stage. In the outside final fitting area, the modules are placed as they will be on site. For Murray Grove, two wings were brought together facing each other across a covered corridor, which provided easy access for components.

The modules left Huntingdon complete with kitchens, including fridge, cooker, electrics and plumbing for a washing machine or washer/dryer; a bathroom, shower and toilet; built-in wardrobes, wall finishes and floor coverings. The flats will be ready for tenants to move into as soon as the exterior works are completed and service connections made.

Contractor Kajima completed the foundations at the Hackney site in February, and in March the first 35 modules were placed to five-storey height in just three days. Another 30 followed in April and the last nine were installed in May.

The balconies are now being built, then exterior cladding will be clipped on – terracotta on the street side, timber on the garden side. The access decks, entrance tower, terraces and service connections will also be built. Altogether, time on site is expected to be around six months, with handover to the Peabody Trust set for August.

Progress at Murray Grove can be followed on Yorkon’s website, which is updated several times a day with pictures from an on-site camera, at: www.webcam.yorkon.com