Need affordable homes fast? How fast? Is three hours fast enough? What? You want fast and cheap? How cheap? Wait a minute, here, read this article
It is 6.30 in the morning and a team of workers on a Norwich building site are looking out at an empty house plot, mugs of coffee in hand. Three hours later, they've got the kettle on again and the plot is filled by a rather ordinary-looking three-bedroom semi, with its interior so complete that low-energy bulbs are already fitted into the light sockets.

In the intervening time, the site team has barely had to work up a sweat, as most of the graft has been done by a mobile crane and a team of factory workers in Sheffield. It is an anticlimactic finale to two years of co-operation between seven organisations working in partnership.

The strategic partnership, collectively known as Folio, has generated the UK's first two-storey timber modular housing scheme: 10 semi-detached houses built from just two modules then conventionally clad and roofed. Folio's objective wasn't to get into the construction industry record books, however, but to come up with a modern method of construction for housebuilding that would please the Egan efficiency objectives and the constrained budgets of the affordable housing sector.

The partnership was initiated by the eastern region registered social landlord Flagship Housing Group, working with module manufacturer Omar, contractor Lovell Partnerships, and a team of consultants. Co-operation has been the key to success. "We all sat down on day one and discussed what we were all trying to achieve," says Martin Aust, development director with Flagship.

In fact, the initiative puts into practice the advice of Manufacturing Excellence, the Housing Forum report into off-site manufacturing in housebuilding published earlier this year.

"We found there was a mismatch between manufacturers and developers that was holding each back," says Tim Venables, one of the report's authors and a researcher at Imperial College's Tanaka Business School. Each has a different business driver and business model: at its most basic, manufacturers' require long guaranteed production runs to lessen unit cost whereas developers needs to be free to react to short-term changes in the market. With Folio, the manufacturer knows it has continuing demand for its product, as Flagship has committed itself to building 100 units a year (about 14% of its development programme) using the technology.

The Flagship Housing Group and its team began the initiative by looking at the more commonplace methods such as timber frame and steel modules. "We spent a long time talking to manufacturers. They had lovely products but they were ultimately impractical because the costs were too high," says Aust. "We wanted a demonstration project that had a real potential to deliver a long-term programme."

Timber modules offered the advantages of familiarity of material and cost-effectiveness. "This was something we knew and understood. This worked with what we do," says Liz Robinson, of employer's agent Oxbury. The module maker is Omar, not a company widely known to the housebuilding industry – although technically Omar does build homes, albeit of the slightly kitsch park home variety. But Omar's park homes differ from more permanent structures in key ways. Most crucially, they do not have to comply with Building Regulations, so for this initiative the timber modules have been strengthened to attain compliance and withstand transportation from Omar's factory to site.

Unlike their counterparts in steel modular housing, Folio also opted to work with large modules, up to 4.6 m wide. "That was because we didn't want the occupants of the homes to see a lot of joins," says Robinson. However, the size of the modules meant they had to be transported with a police escort, now required for loads more than 4.1 m wide.

The Norwich project is only the first phase of Folio's evolution: 15 sites are planned over the next two years. The next, a 28-unit scheme in nearby Thetford, goes on site within the month and Folio will then be ready to market its approach to other clients with a series of unit types. These are two-, three- and four-bedroom houses, two- and three-bedroom conventional and disabled bungalows and one- and two-bedroom apartments. "We've tried to maximise flexibility, so for the apartments you simply add another module to generate the two-bedroom unit," says Jon Boon, partner at architect Ingleton Wood.

There have been teething problems, notably in getting the site-finished brickwork to align around the factory-fitted windows, but the partners are looking at improvements such as slimming the modules to eliminate the need for a police escort. They also want to find an alternative for the polythene wrapping used to protect the modules in transit, which is not just wasteful but downright eco-unfriendly. And they are hoping to cut build time by carrying out site infrastructure works while modules are being made, and by getting a pair of house modules into position in a day on the Thetford project.

Most important of all, real build costs are meeting the partnership's predictions. "It varies from scheme to scheme, but all are so far comparable to traditional build, and within Housing Corporation total cost indicators," says Simon Medler, regional manager for Lovell. The team is enthusiastic about the prospects for this latest venture in modern methods – except, that is, for the site workers who have a 6am start …

Folio Partnership

Client Flagship Housing Group
Architect Ingleton Wood
Employer’s agent Oxbury & Company
Building Regulations issues Norwich council
Structural engineer Richard Jackson
Manufacturer Omar Homes
Contractor Lovell Partnerships

Step one: 6.30-7am

Low loaders arrive early (to avoid congesting the roads) at the site in Gipsy Close, Norwich, carrying the ground- and first-floor modules that are to form the semi-detached house. They are fitted (down to the low-energy lightbulbs) and polythene-wrapped to protect the walls’ breather membrane. The plot has already been prepared with 150 mm block foundations and scaffolding is in place.

Step two 7-7.45am

The ground-floor module is craned from the lorry over the scaffolding and onto the plot. Modules for a two-bedroom house weigh 4.5 tonnes and for a three-bedroom house about 6 tonnes. The walls are made up of insulation within wall studs, finished externally with a 9 mm layer of plywood. A service void is formed by adding 25 mm battens to the inside of the walls, and this is finished in plasterboard. The ceiling to each unit is formed from 100 mm joists with a plywood topping. Doors and windows are put into modules in the factory, along with all kitchen and bathroom fittings, stairs and services. Ceilings are finished in plastic Artex with coving around the perimeter to allow for movement in transport. The stack pipe connection is fitted as the unit is being lowered into place. Services and waste connections protrude from the module so the brick exterior can be built around them.

Step three: 7.45-8.30am

The first-floor module is craned from the lorry and positioned on top of its ground-floor sister. The modules are not bolted to the foundation or to each other, they are tied into the brick skin. Units are aligned by the stairwell, with an operative standing on the lower part of the stairs as the first-floor unit is lowered, guiding it into place. Only the perimeter wall of the upper module is in contact with the lower one, so only perimeter walls are loadbearing. Elsewhere there is a 14 mm gap between the modules, which is concealed internally by a cladding strip around the stairwell. The banister, top riser and the last section of stair string are also fitted on site.

Step four: 8.30-9.30am

Timber plates are positioned on top of the first-floor modules for the roof trusses to rest on, so the roof load is again being taken by the perimeter walls.

Step five: Rest of the day

The roof trusses, gable-end and party wall panels are lifted into position and the roof is prepared for tiling. Bricklaying starts when the roof is finished to ensure that the structure is fully loaded and to guard against movement cracking. Total build time is eight to 12 weeks.