When Butlins decided its three surviving holiday camps needed more undercover facilities, it soon became obvious that a tensile fabric solution offered many potential advantages. 'We needed a new image, something with a special character and a striking appearance,' says Keith Hawkswell, property and development director for Butlins parent Rank Holiday Group.
'But above all, we had to have a solution that involved minimum disruption to the camp's operations.'
The objective was to roof over the central open spaces at the Skegness, Minehead and Bognor Regis Family Entertainment Resorts. The problem was that the spaces were surrounded by existing buildings, some of them 60 years old or more. Budgets did not allow for disturbance or alterations to the structures. And closure of the camps for more than a few months at a time was not on the agenda.
Butlins was also looking for an attractive structure which blended in with the resorts' seaside locations.
Hawkswell admits he was pre-disposed towards fabric structures - he has long admired the fabric canopy over a bandstand near the company's Hemel Hempstead HQ - so he welcomed architect S&P's suggestion that a tensile fabric be used.
Working with structural engineer Buro Happold, S&P drew up plans for 'mini-domes' covering up to 7,500m2 - the size of Wembley Stadium's football pitch. Ten steel masts support the largest, at Bognor Regis, while Skegness requires only five. Plan geometry is determined by existing buildings and varies between sites. These, the biggest such structures in the UK after the Millennium Dome, gave Butlins what it wanted - 'a strong, marketable seaside image with a suggestion of white sails', and 'striking landmark structures'.
Technically, these were far more complex to design and build than might appear, says fabric contractor Landrell managing director Lance Rowell. 'Because of the surrounding buildings, there was no way we could get away with a simple tent, with fabric loads taken straight down to the ground.
'Instead, there had to be a ring of perimeter pylons to anchor the canopy and allow free access to the buildings from the covered area.'
'Marshy coastal' ground conditions at all three sites dictated piled foundations under pylons and masts. Fabric choice was a tougher decision.
'We wanted the most translucent fabric possible in a colour that did not make people inside look bilious. There was also the question of initial cost versus life span,' says Hawkswell.
'In a decade or so fashions might change and there might be more advanced fabrics available.'
So the obvious choice was polyvinyl chloride-coated polyester, the fabric originally chosen for the Millennium Dome and later rejected in favour of longer lasting Teflon-coated glass fibre. Lately, PVC-based materials have come under sustained attack from environmentalists, but Hawkswell says the choice was made only after considering environmental issues.
Buro Happold chose 1.6m x 1.6m lattice braced trusses for the masts, formed entirely of circular hollow section steel and weighing 25t. Perimeter pylons cantilever 3m over existing buildings and vary in height between 6m and 16m. Pylons weigh up to 30t each.
Individual fabric panels - up to 2,000m2 - are joined by tensioned steel cables in pockets at the valleys. Only 11 panels are needed, even for the largest roof.
Construction on all three sites was in two relatively short phases, with piles installed in the first three month phase last spring and masts, pylons and fabric in a five month final phase. Ground works for the three structures cost £6M out of a total cost of £23M, and all three were effectively complete by the end of last month.
'Although we could not have justified the cost of conventional structures this size, cost was not the real constraint, it was logistics,' Hawkswell says. 'And apart from the minimal disruption, the speed at which the site became weatherproof was very impressive.'
When they open to the public this Easter the three new 'Skyline Pavilions' will offer year-round all day entertainment, from street theatre to circus acts. Butlins' £139M investment in the relaunch of its
core resorts is intended to make them attractive to customers in the growing short break market. and it is the flexibility of the space beneath the fabric canopies that will be the secret of its success, the company believes.