The Housing Corporation echoed Ford's philosophy last month when it announced its accreditation process for standard housing templates. The argument goes that it is hugely inefficient for social housing providers across the UK to produce bespoke designs, all of which have to be approved by the corporation. The corporation believes that standardising components, layouts and manufacturing processes will save money.
Off-site housing manufacturers have already responded to this initiative and produced a range of standard templates. Volumetric manufacturer Yorkon has had three designs approved, as has Advance Housing. But Space4, a subsidiary of housebuilder Westbury and the UK's largest producer of prefabricated housing, has thrown its hat into the ring with 17 housing templates, which it hopes strike a balance between choice and efficiency.
Housing associations are not compelled to use the corporation's standard templates, but if they do, approvals may speed up and costs come down, making it difficult for cost-conscious associations to resist standardisation.
"I believe it will reduce costs, as there is too much reinventing the wheel each time in terms of design," says Brendan Ritchie, innovations director of social housing contractor Willmott Dixon. "Anything that creates more volume will help the manufacturers cut costs."
Ritchie points out the templates only apply to interiors, meaning homes won't end up looking the same.
Space4 sees standard templates as a way of making homes cheaper. "We commissioned a range of housing templates incorporating Housing Corporation design standards," explains managing director Patrick Dorman. "These were designed to be [Housing Corporation] compliant but also to support optimum efficiencies. In other words, to make them as simple as possible for our manufacturing process and therefore more economical for our customers."
The firm worked with social housing architect Calford Seadon on the 17 accredited housetypes.
The factory can make 6000 timber-framed four-bedroom houses a year. Of these, 2000-2500 are earmarked for Westbury. But to make a profit, the factory needs buyers for its remaining capacity, and social housing providers are important customers.
"We are a high-volume producer," says Dorman. "Our profitability is totally governed by volume. We expect to be in a break-even position this year [by March 2004] so we need the running rate in the second half of the year to achieve that."
Space4 produces a panellised whole house solution (see "How Space4 builds a home, overleaf). The factory's flowline production process has been designed to be highly efficient yet very flexible. The computer-controlled line can produce different housetypes in any sequence. Fundamental changes to the homes' specification – for example, changes dictated by new building regulations – are accommodated in "a matter of hours", according to Dorman.
The 17 templates were designed to suit the factory's overall manufacturing process. The key is to juggle the wall configurations of individual homes to fit the company's standard production unit, called the multiwall. The factory has been configured to produce multiwall panels 12 m long. These are then cut to the right length at the end of the line.
This is comparable to calculating how to cut up a sheet of standard-sized mdf into the maximum number of useable pieces. At Space4, any offcuts can be made into new panels, but the social housing templates have nevertheless been designed to get the most possible out of each multiwall. According to Dorman, the utilisation rate for each multiwall is 85% for homes that have not been designed for manufacture, but 90% for the social housing templates.
A second way of improving efficiency is making the houses faster to build once they reach site. As Space4 also erects every home it makes, it has identified ways of making the corporation-standard housetypes quicker to build. For example, each floor is made up of several floor cassettes. "It's more efficient to have as few cassettes as possible," explains Dorman. "You can save 15 minutes on site by having one cassette fewer." This may not sound like much, but when you consider you build a house in a day, it's quite a lot."
The bathrooms, cloakrooms and stairs have been standardised, too. "This proposes an opportunity for a pod and panel concept for bathroom fit-out if there is sufficient demand," says Dorman, adding that a second plant for standardised pods is a distinct possibility.
However, he emphasises that Space4 hopes it has struck a balance between standardisation and individuality. "We have made sure these are not inefficient houses, but we have not gone to the utopian efficiency of a grid that is so inflexible that our customers wouldn't want them."
Willmott Dixon's Ritchie has also spotted the potential of standardised templates. The company sources some homes from Fusion, which makes a panellised product similar to Space4's, albeit metal-framed. "If you are standardising the room layouts it's logical to standardise the services," he says. "You know where the plumbing and electrics go so there is the potential for fully enclosed walls with services already installed. Currently that can't happen as the decisions aren't taken early enough in the process."
Dorman believes off-site manufacture will ultimately be cheaper than traditional construction, although in common with most homes built off-site, Space4 products are marginally more expensive in construction terms. "There is a favourable cost trajectory [with off-site ] when you consider ongoing legislation and contractors' inflation rates," he says. "Sure, we will have to add more materials to meet future regulations, but this will be cheaper than the conventional alternatives."
Ford's vision of a mass-produced future for cars is slowly becoming true for homes.
How Space4 builds a homeWestbury set up Space4 because of growing skills shortages, constant changes in Building Regulations and a desire to build homes more quickly. The housebuilder commissioned the Warwick Manufacturing Group, based at the town’s university, to help ensure the factory was efficient and flexible. It also studied off-site manufacturing techniques in Japan, the USA and Europe.
The end result was a factory based on flowline production. In other words, components enter the factory at one end, are assembled on a constantly moving production line, and emerge at the other end as the finished product. Most other off-site manufacturers rely on batch production, which involves manufacturing batches of sub-assemblies, then putting them together – also in batches.
At Space4, architects’ designs are fed into the company’s CAD/CAM system which controls the machines making the panels. This is linked to “enterprise resource planning” software, which converts the design into a bill of quantities. Suppliers can access Space4’s intranet over the web, so they can see the bill of quantities and work out how many materials are needed, and when, and deliver them just in time.
The standard unit of production is the 12 m long multiwall, which consists of several sections joined together. The configuration of each multiwall is supplied to the operator of the multiwall assembly machine. Using the CAD data, the operator positions each timber stud in place and the machine fixes the frame together.
The panel then moves through the factory on an automated line. The next stage is to fix the cement fibreboard used to stiffen the frame. CAD data controls a machine which cuts the board to the correct size, and this is stapled to the frame. The frame is then automatically flipped over and a polythene sheet attached to the other side. Internal walls are made on a parallel line and do not have polythene attached. Instead, they go straight to the end of the line ready for cutting up into the correct lengths.
The polythene is needed to contain the foam insulation used for the external walls. The panel moves into a massive machine that injects phenolic foam into each void. Controlled by the CAD/CAM program, the machine injects precisely the right amount of foam into each void. Once the foam is cured, the 12 m multiwall is cut into sections and leftover timber is sent to the beginning of the line to be made into a new panel. Doors and windows are installed and the wall panels put into racks in the right order for dispatch.
Each home is built on a concrete pad foundation. The roof is made up on the ground from conventional trusses, unless it is a “room in the roof” design, an option that Space4 can offer. The wall panels are transported by lorry and four workers assemble the home. The ground-floor walls are assembled first, then floor cassettes are positioned, the next storey is built and finally the roof is craned on.