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Cowlin rises to the hillside challenge

SCHOOLS

Jutting out of the hillside in one of Bristol's most af. uent suburbs, the Redlands Green School is a design statement procured by the council through a partnering framework with local contractor Cowlin Construction. Joanna Booth went on site to learn more

THE PLANTED roof will snake out of the ground, and the matt black and brown wall tones will blend into the hillside. Redlands Green School is being built on green space ? which evidently raises planning concerns ? and Bristol Council was keen to ensure that it did not present an unsightly edifice where there was once a majestic view over the city. So, instead of levelling off the sloping site, the school has been designed into the landscape.

Even equipped with a low-impact design, the school was stalled at planning stage.

'Despite the real need for a school in this area some people didn't want it in their backyards, ' says Neil Sher reard , Cowlin regional managing director. 'Its necessity had to be proven and environmental studies undertaken. There was a freeze for six months while it was negotiated.' Finally starting on site in June 2005, the structure is beginning to resemble its f inished shape. Despite the original slope of the ground level, a substantial muckshift was still required, removing 24,000 cu m of spoil and remodelling the ground. The underlay is limestone and parts of the building could bear on traditional foundations, but some CFA piling was required, especially under the multistorey areas.

Within six buildings ranging from one to four storeys, Cowlin Construction has to build to 17 different f loor levels as the school meets the gradient of the ground.

'It meant a lot of revisiting during the design process, ' says Neil Spurway, Cowlin contracts manager. 'If you tweak one area it affects another.' With wheelchair access a necessity as the new establishment will absorb kids from a nearby special educational needs school, a multi-level structure would not seem to be the logical solution.

'There's a central street, which is user-friendly for those with physical disabilities, running down between the buildings and most facilities are accessible off that, ' Mr Spurway explains.

The building is a reinforced concrete frame in all areas over one storey. Top f loors and single storey areas are steel framed. The block containing the sports hall uses a composite system, which is not stable until all trusses are in place and all slabs cast ? until then is extensively propped.

The structure follows complex curves on many different planes. 'There are plan curves, section curves ? everything is on a curve, ' Mr Spurway says.

'We couldn't have done it without computers.' The ent ire school is clad in impor ted Canadian cape cod timber, which has been well dried.

'It doubles the working life span from 25 to 50 years, ' says Nigel Lovett, Cowlin project manager.

'It's in two colours: matt black and curry brown ? that's the off icial name of the shade.' The three classroom blocks to the south of the central street will use a standing seam roof system f rom Kalzip. Though the roof sect ions are st raight, the roofs curve in waves. The central street is covered with an ETFE ? ethyltetraf luoroethylene ? covering supported on steel trusses. Inf lated cushions of this transparent polymer, most famously used on the Eden Project, will be used to balance the heat and light passing through it.

While being built as six separate buildings, the school will eventually look more like four. All three blocks on the northern side of the central st reet area will be linked together under one green roof. On top of the concrete roof slab much of the area is covered in sedum, which will help to control water run-off on the site. Some turfed areas will be used as outdoor classrooms.

Access will be located at the top end of the site, where 6,000 cu m of excavated spoil will be used to form a ramp from the school entrance on to the roof.

Giving child ren access to a roof that at its far end towers four storeys above the ground presents an obvious problem. 'The hand rail system is in the middle of being designed by the architects BDP, ' explains Mr Spurway. 'The initial format was rejected on safety against cost issues, and because it made it look rather like a prison. It will be done with care.' The green roof is par t of the school's water attenuation system. A landscaped open ditch in the grounds will store excess water temporarily, allowing discharge rates to be balanced. The site is f lanked on three sides by allotments and those located at the downhill end were not keen to become a run-off stream for the school's water as it makes its way to the outfall 30 m further down the hill.

To prevent this a 150 m-long tunnel is being drilled from the base of the site underneath the allotments th rough wh ich water will be discharged at a controlled rate. 'It has to be drilled from the top end down, ' explains Mr Spurway. 'And then the line has to be pulled all the way back through without collapsing the tunnel. Inside there will n See page 28 n From page 27 be a medium-density polyethylene pipe.' The environment was a major concern at planning stage. Being built into the side of the hill allows the building to maximise energy efficiency by using the ground temperature of the envelope. Natural lighting and ventilation are used where possible. 'It's about striking a balance between ventilation and acoustic t ransfer, light ing and heat gain, ' explains Mr Lovet t.

The presence of a badger sett on site, though cordoned off, means that no excavation can be left open overnight without a means of exit. Many of the original trees on the site have been retained ? even the two on either side of the entry point. A special ramp has been constructed to ensure that site traffic does not crush the roots of the copper beech and the poplar that f lank the access road. There is little space between them. 'We had fun and games getting some of the trusses in, ' Mr Lovett recalls.

Traffic control and management have had to be carefully managed , especially as the road f rom which the site is accessed is a private one. 'We've made sure every thing runs smoothly, ' Mr Sher reard says. 'The council's director for education lives in the apartments over the road, so there's an even greater incentive.' Cowlin is currently delivering schools projects worth £65 million in the south-west, including another scheme in the same partnering framework as Redlands Green School. It has also delivered £40 million-worth of work for Bristol University over the past four years.

Cowlin is involved in four PFI schemes, but as a contractor rather than as a financial equity holder.

'We're a builder, not a developer, ' Mr Sherreard says.

Bristol raises the game

A COMBINATION of poor grades in the state system and relatively prosperous parents had left Bristol City Council with the highest rate of private schools per head of pupils in the country.

But an ambitious build programme of new schools is part of the council's plan to bring children back into state education.

Bristol City Council has a partnering framework with Cowlin and architects BDP to deliver not only Redlands Green School, but also Fairfield school, another secondary that is almost finished. The funding for these has been provided by the Department for Education and Skills, the Leaning Skills Council and Bristol Council. A further eight secondary schools are being procured under a PFI scheme.

Excitement among parents in the aff luent Redlands area is running h igh at the prospect of a plush new state school. Neil Sherreard says that a number of business contacts rang him while the school was in the planning stages, trying to get an inside take on whether it would go ahead. 'People were thinking of moving to get their kids into an area with a state school. If this went ahead they wouldn't need to.'

Bristol born and bred

COWLIN Construction has a long history in Bristol. It was started by William Cowlin in 1834 and stayed in the family until a management buyout in 1989. The shares remain with the operating directors. 'It means that decision-making is quite straight forward, ' says Mr Sherreard. 'We can be very hands-on with clients at the highest level.

There's very little middle management.' Cowlin now works across the whole southwest, with offices in Bristol, Cardiff, Exeter, Plymouth, Southampton and Yeovil.

Turnover last year was £150 million and is set to rise to £190 million th is year. 'In the next th ree years we will increase to over £200 million, ' says Mr Dalton. 'We are a significant player, competing with nationals and other large regionals.' Education is a particular focus but the base of work is broad, encompassing health, commercial, residential, retail and leisure.

Cowlin has strong track record in refurbishment and can find itself revisiting a structure it built in the first place.

'Cowlin started building Bristol's council hall in 1938, ' says Mr Dalton. 'There was an unavoidable break through the war years and then it was finished in 1950. We're now working on a four years refurbishment package there.'