St George is a huge private estate for the ultra-rich surrounded by private security guards, where the enormous houses are barely visible at the ends of their long driveways. Mixed in with standard suburban homes is the Mercedes-Benz of prefabricated living, the Huf Haus.
Huf Haus sits comfortably in this environment because of its high technical and architectural quality. And it is physical proof of how out of touch critics of factory-made housing are. For a start, this German system is tried and tested, having been around since 1912 and in the UK since 1996. And it not only looks smart, but is made using state-of-the-art production techniques to a high specification.
Until now, Huf Haus has supplied only wealthy private individuals, and recently announced a deal to build nine £1m homes for housebuilder Wates in London, however it has plans to move into the commercial market with offices, a rugby club and a retirement home.
Wates decided to use Huf Haus for the £1m homes after researching the system. Paul Phipps, managing director of Wates Homes, says: "The Dulwich site is first-class and it justified a more innovative approach. It's an educated market; and why replicate what's there already? The emphasis with Huf Haus is the glazing and the amount of light brought into the home compared with brick."
The other thing that swayed Wates was the system's pedigree. "It's a proven product," says Phipps. "We wouldn't want to put such an expensive site at risk with pure innovation."
The key to the system is its beam-and-post construction. This is an ancient method brought up to date using modern production techniques. Large 220 mm2 posts are connected by beams to form the structure. The spaces between the frame are filled with glass or solid panels.
The system as a whole is not suitable for agoraphobics: generous areas of glazing create light, spacious interior, so the occupants are more conscious of the outside.
The other benefit of the beam-and-post construction method is that it offers great design flexibility, especially with room layout.
Third-generation family member and architect Peter Huf, who doubles as director of the UK operation, designs each house. The ones in St George's Hill are based around a bay system, one bay being the width between two structural posts. A 185 m2 three-bay house is the minimum size, with no maximum. The system allows a wide range of choice of services and fittings – for example, three different heating systems can be specified: conventional radiators, underfloor heating and a forced air system. Solar panels can be incorporated into the roof and external remote-controlled blinds can be specified. Peter Huf will even select and obtain the furniture.
The company designs, makes and builds the house in one seamless process. All the developer has to do is find the land and provide the finance. Phipps found this appealing: "It's a complete housing system, not a timber-frame structure with a veneer put onto it." The design is drawn up using a CAD package that feeds straight into a CAD/CAM system. Here, the architect's design is used to guide the computer numerical control machinery that makes the components of the house. These are produced at the company's factory in Germany and brought over to the UK complete with the workforce to erect the house.
Peter Huf does not see prefabrication as an easy way out of the skills crisis. The company employs 300 skilled people and does not use subcontractors. Huf Haus also takes 30 apprentices each year onto a three-year training programme. "Our capital is our people," says Huf. This approach means workers are familiar with the system both in the factory and on site, thus ensuring a high-quality product.
The production process is concentrated in the factory for quality control. Glulam is used for the beams as they are strong and dimensionally stable. The beams and posts, made up as prefabricated units up to 12 m long by 3 m high, are fitted with glass and solid wall sections in the factory. "You can't get the same quality on site, so we do everything in the factory," says Huf. This also minimises the time spent on site.
The first stage in the construction process is the concrete basement. This takes a week to construct. A raft foundation is prepared on site ready to receive the factory-made precast concrete panels that form the cellar walls and ceiling. The panels are hollow in the middle; once they have been erected, the gap is filled with concrete to create a homogeneous concrete box.
One of the facts that struck Phipps was how well engineered the system was. "The quality and the precision of the factory and the engineering is immensely impressive." The whole house is constructed to a tolerance of ±5 mm, "and by the time the basement is built, the other components have already been made," says Huf. "You cannot adjust the house to fit onto the basement. It has to be precise."
The whole exterior envelope is erected in a week. The internal fit-out process takes much longer – about 11 weeks. Huf says this is because there is a limit to how much prefabrication can be incorporated into a custom-built house. For example, the kitchens are all different and the only prefabricated elements in bathrooms are the prefabricated panels that house cisterns and prevent plumbing noise being transmitted through the house.
In the bathrooms, pipes are fed through hollow posts to the upper floors. The internal wall panels have to be installed on site and are made up from timber studwork filled with insulation and finished with plaster.
Peter Huf says he was persuaded to move into the commercial market by approaches from would-be customers. "I truly believe in the free market; it will tell you what it wants," he says. And, ultimately, the market will decide how successful Huf Haus is in the commercial sector.
One reason there are no commercial Huf Haus buildings in the UK is because of the attitude of large business investors, particularly pension funds, towards timber frame. According to Huf, they prefer to see concrete- or steel-framed buildings. But things look pretty rosy on the housebuilding front, as Phipps is sufficiently impressed with the system to consider using it for other prestige sites in the South-east.