Max factory

Bricklayers and conventional mortar played no part in building these houses. The homes' conventional looks belie the fact that they are a UK first - factory-finished volumetric two-storey semis. The historic, slow-to-build, labour-intensive British house has been reinterpreted as two units each of four modules that connect like children's building blocks. Their seemingly solid-brick elevations are actually wafer-thin brick slips glued onto metal panels. Kitchens and bathrooms arrived on site fully fitted and tiled.

Prefabrication, modular and volumetric construction are being trialled by a number of developers, but these houses represent a quantum leap in technology from projects like the Peabody Trust's Murray Grove project in London. Murray Grove's modules are still clad on site; these houses arrived on site 80% complete, took one week "to assemble", and site labour involved little more than adding strips of brick and tile at the interface between modules. One clue to the extent of the culture change here is that the two homes were originally planned as a fortnight's assembly, the programme then halved so that the homes could be complete in time for the co-incidental opening of new facilities by a local politician, one John Prescott MP.

The DETR supremo's Hull constituency encompasses the plant of manufacturer Britspace, a company that is applying the methodology it uses to build McDonalds restaurants to homes. Over the past year it has been working with two development partners, one volume housebuilder, one registered social landlord. Wimpey Homes contributes its procurement and supplier chain expertise to the venture, while The Guinness Trust is commited to developing 50 homes on its sites over the next year.

The homes have been built in the back yard of Britspace's factory in Gilberdyke, east Yorkshire, as prototypes under the partners' joint initiative, which is called P3, proof of principle product. The principle to be proven is factory build, and the partners have their own objectives in seeing that goal achieved. For Britspace the prize is a potential new market in housebuilding. For Wimpey, factory build is one of several routes to Egan compliance being tested, and the P3 initiative involves the kind of housing association tie-up that Egan wants and that could lead to Wimpey being able to offer an improved product to its housing association clients, and perhaps eventually to its market sale buyers.

"Egan maps out housing association linkage because they are purchasers in the first instance - they define the product and are required to meet goals, so it is natural for us to want to partner with a housing association," says Geoff Fermor-Dunman, procurement director with Wimpey Group. Egan is also the imperative for Guinness Trust. "Our objective is to see how consistent this is with our current interest in Egan - whether we can build more quickly and more cheaply," says Mike Cohen, Guinness chief executive.

The unconventionally-produced prototype has deliberately been given solidly conventional looks. "We started with the requirement that if what the customer felt they were being offered was different, in a way that caused adverse reaction, that would be detrimental to its chances in the market," says Fermor-Dunman. "There's a necessary appearance and materials driven product for housing - people want a house to look like a house. What we have got is in no way visually discrepant to the traditional house, and is in most regards better. It is of higher quality and has better dimensional stability over time."

The prototype houses are a new design, "a marriage of Wimpey kerb appeal and Guinness Trust's design requirements," according to Graham Townend, commercial director with Britspace. "They are built to the Guinness size and specification, but using materials in the Wimpey supply chain, to give Guinness price benefits." The design complies with Housing Corporation scheme development standards and takes into account Guinness' priorities. "Because it is tenanted it needs to be very robust, and we are sensitive to wanting to keep maintenance costs to a minimum and to minimising energy costs on tenants' behalf," says Cohen.

Britspace broke the house design into modules that would be suitable and most efficient for mass production. "We handed a bathroom so that it was more or less above the kitchen to give a single service route through the houses, and moved walls slightly for the module size," says Townend.

Most materials used to build the houses are familiar. The modules and their accompanying roof panels are made from cold rolled galvanised steel. While the modules' external walls are factory-finished in brick slips, roof panels are topped in granite-faced steel roof tiles. "They are used widely by housing associations for refurbishment and were desirable here because they were only around a seventh of the weight of a concrete tile," says Fermor-Dunman. "These houses use traditional materials in a traditional way, but are built in a factory. The difference is in the process rather than the materials. When you build in a factory in modules it does not impose restraints in materials."

Partners have now to measure the house against those Egan targets and more as they refine the prototype. Energy efficiency, noise transmission and other aspects of performance will be tested, as well as the reaction of warranty providers and mortgage lenders. Developer partners are discussing a 60-year guarantee with Britspace.

Wimpey will assess potential homebuyer reaction, although Fermor-Dunman will not say if and when the housebuilder will develop the homes for the private market. Still, Wimpey is sufficiently impressed to be considering trialling similar modules for apartments. Already, the initiative has brought the developer partners into contact with a very different culture. "When we asked Britspace how they dealt with maintenance issues on McDonalds projects, they gave us a puzzled look and said that things don't go wrong," says Tony Clipstone, regional director with Wimpey Homes. "It has not been like traditional construction where you have separate trades doing separate tasks," says Guinness' Cohen. Guinness also benefits by getting a more flexible home with usable roofspace. "Our first go at factory build looks very successful. I'm a convert to this," adds Cohen.

But the success of P3 will also depend on cost. "The cost will depend on the volume," admits Cohen. "It doesn't look as if it is going to be more expensive, but we need to be producing up to 500 units to get the economies of scale."