Centre stage

the striking blue cladding of The Zethus Centre on the University of Greenwich campus in Dartford, Kent sets the stamp of its role as a showcase for new housing technology and a standard-raiser for the entire housebuilding industry (Building Homes September 2000). As a focus for education and training activities and the first UK centre to co-ordinate research and development on housing innovation, (see page 38), the innovations in the centre building itself are integral to the message.

SmartClad cladding, which while superficially resembling traditional clapboarding, is in fact an engineered wood siding supplied panelised or in strips by one of the centre's lead partners, Louisiana Pacific. Engineered timber is well established in the North American market but is still something of a novelty in the UK. Louisiana Pacific also contributed I beams for the roof, OSB flooring and OSB sheathing for the timber frame walls.

The concept design for the building was by architect Calford Seaden but the detailing was handled by the centre's co-originator, consultant The Palmer Partnership, and notably Geoff Pitts who was for many years chief architect at the Timber Research & Development Association. The building reflects many TRADA ideas, none more so than the reverse wall. "We developed the reverse wall back in the early 1990s," says Pitts. "However the market has never really been right for it until recently. The big idea is to switch the arrangement of the timber frame wall so that the bracing layer is on the inside where it acts additionally as a vapour control layer, facilitates air tightness and virtually eliminates the need for support noggins. And having a layer of OSB under the plasterboard makes for a far more robust structure, better suited to many of the registered social landlord clients we anticipate will want to use it."

The reverse wall design has already been adopted by Beazer Partnerships in its Tee-U-Tec system, used to make wall cassettes. The Zethus Centre version is being fitted with Kingspan phenolic boards, overlaid by Proctor's Frameshield and the SmartClad systems.

The building is being largely built on site. Where prefabricated panels are used, they are generally made up and manoeuvred directly into place. "It's a halfway house between stickbuild and prefabrication," says Pitts. "It's particularly well suited to buildings where there are few repetitive parts. We haven't had to use a lot of heavy plant. For instance, the roof I beams are so light they don't require craning."

Asphalt shingles provide the roof cover on the octagonal exhibition hall in the centre of the building with vertical softwood planking on the two wings. Pitts explains: "Buildings put up in the 1980s with this roof detail continue to look good and I estimate it will last 25 years. The key to its success is to use a high performance breathable membrane, in this case Daltex Roofshield, with a drained and vented cavity between it and the roof cover."

Unlike many flagship green projects, Zethus doesn't reject the use of PVC. The joinery is a mix of site-made Finnish imports and locally fabricated PVC. "The reality is that PVC is what a majority of housing associations want to use so it seems pointless to reject it out of hand." The Finnish windows on display are a typical Scandinavian triple-glazed design, clad in powder coated aluminium, and the favourable exchange rate makes them increasingly affordable.

Other innovations showcased in the centre include Roger Bullivant's piled foundation system which supports a suspended hollow core floor. On top of this sit 63 mm-deep battens packed with Kingspan's polyisocyanurate insulation. The floor is covered in another engineered timber product, NuWood, this time from New Zealand. Its patented mix of pine dust and a number of organic ingredients – one believed to be semolina– has much of the strength and attractiveness of hardwood flooring at far less cost.

Just how well it wears should be apparent to all who visit.