Technical Offsite and M&E

block flats with supporting steelwork, we’re probably more expensive,” acknowledges Battle. But de Waal is quick to put that in

context. “Much more so than with traditional build, with houses that embrace MMC the price is more connected to volume. With 10 homes, you’re not really generating the right level of pricing for MMC. But if we get an order for 1,000 units, we can go out to Sterling, Fusion and the supply chain with that certainty and they can price it in for perhaps 50% savings in construction cost.” The production timescale would of course also drop. The team also points out that with the

to “nail” M&E and fit-out too soon. Fusion’s lightweight steel gauge frame

arrives pre-boarded with insulating infill to create the floors, load-bearing internal walls and roof, creating a watertight external envelope and removing the cladding installation from the critical path. Finally, the pitched roof is constructed from a lightweight steel frame, and covered with a zinc coating, although it’s not yet clear whether this would be applied in the factory or onsite.

Don’t mention the “c” word The cladding system relies on 80-90 different panels for a typical house, hooked onto the frame. Joseph Cefai, founder director of precast specialist engineering firm Sterling Services, shies away from the “c” word. “We don’t want to talk about concrete, people think ‘grey’ and ‘prison’, so we call it architectural precast,” he says. The panels are made from a clay stent, taking on different colour tones according to the type of aggregate used: Spring Vale, for instance, uses three different cream and yellow tones. Cefai notes that there are no proprietary secrets in the panels — in future, any other supplier could replace or join Sterling in the supply chain. “But the ethos has been ‘we’ll invest in you if you invest in us’.” At Spring Vale, the supply chain is

responsible for the structural shell, but Willmott Dixon, as main contractor, is

42 | OCTOBER 2013 | CONSTRUCTION MANAGER

preparing the site and foundations, fitting out the shells and completing any external works. For Spring Vale, Willmott Dixon has

calculated a build time of 33 weeks compared to 45-46 weeks for a conventional build. The Rational House project is also allying BIM technology to MMC. Fusion, Sterling and other subcontractors contribute Revit-designed components to an integrated design model, which Aecom then links to the BIM Measure package to rapidly calculate detailed cost plans. On cost comparisons versus traditional

construction, Battle and de Waal first ask the question: “What is traditional construction?” “We get asked this all the time, and the answer is ‘it depends’. If you’re talking an industry-standard 2.5m from floor to floor family house with a conventional slate roof, or for brick and

The Rational House story is quite complex. The intellectual property in the design originated with Tim Battle and architect Bob Dalziel, who established Rational House Ltd. Aware that the pages of the Architect’s Journal are full of architect-led modular housing systems that remain forever at prototype stage, the duo brought in Aecom and Willmott Dixon to advise on commercialisation, buildability and supply chain issues. Rational House then licensed the design to a new

company, City House Projects, which is now in contract with Hammersmith & Fulham council to provide design, planning and construction services. Dalziel and Battle

Rational House meets the call for the “new London vernacular” by echoing Georgian and Victorian terraces, but applying 21st century design and technology

market recovering and talk of labour and material resources being stretched, their guaranteed supply chain and lower onsite labour costs could start to skew the cost analysis is their favour. “There’s a constant drive for fixed price contracting — contractors that can’t fix their costs increase their risks and that makes the product more expensive. But we can give clients certainty during the tendering process,” says de Waal.

Hammersmith was certainly convinced by the Rational House proposition, aware of the need to create more middle-market housing in its increasingly polarised post codes. The borough was also keen to embrace new forms of technology and work with integrated supply chains. “Hammersmith & Fulham have been on the journey with us, but as people see Spring Vale go up, it’s possible that other London boroughs will be interested. But the last thing we want to do is go out and grow too quickly then fail because of supply chain delivery problems — that’s been a typical problem with MMC in the past,” notes de Waal. CM

Rational thinking leads to an integrated team

retain a role in concept masterplanning the actual projects, but detailed design will be delivered by Aecom’s architects. Battle, de Waal and Joseph Cefai are all keen to

stress that Rational House is a team drawing on a wide spectrum of skills, experience and support, rather than ego-driven designers or messianic MMC flag-wavers. “Having been in the industry all my life, I’m determined this should be a collective endeavour,” says Battle. “We’re working as a dedicated team, it’s not four

separate companies asking ‘who’s responsible for this?’ or playing the blame game. With Revit as the integrator, the feeling is we’re one team,” concludes de Waal.

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