This month, a range of roofing solutions for a college, radio offices, a dream home, a sustainability-focused extension and a stadium...

A Because it sweeps and curves

Readers may recognise Dartmouth’s Leigh Academy building from our project report in the April 2007 issue of CM. Now complete, the scheme’s four college blocks are covered by a large, sweeping aluminium Kalzip roof that arcs down from a height of 12m.

Designing the complex roof required close collaboration between main contractor Galliford Try and roofing contractor Lakesmere to maximise airtightness and ensure that U-values were kept in line with the latest Part L regulations.

Installation provided its own headaches. The purlin-free roof required large deck spans of up to 9m – too big to be manhandled or fork-lifted – and space constraints made access very difficult; Lakesmere therefore designed special brackets to crane the decks into position. Three-dimensional modelling software also helped ensure accurate detailing of the curtain wall section windows installed within the curved Kalzip.

‘The key factors in the roofing material were its technical flexibility, overall aesthetic appeal and its ability to meet the required u-value and airtightness rates,’ said a spokesman for architect Building Design Partnership.

B Because it's natural

When specifying materials for his new dream home in Norfolk, architect Nigel Lyles knew the tremendous roofscape, which comprises several roofs of varying pitches, would define people’s first impressions of the building.

So rather than choosing a machine-made product, he opted for a natural hand-made range of Keymer’s Shire Heritage clay tiles.

On a roofscape of 35,000 tiles, the full colour range was specified – Downs Red, Heritage and Priory. The blend was designed to fit seamlessly with the Norfolk locality, to mirror a traditional country home and the building’s handmade brick walls. Planners had also insisted on handmade materials because the project was located in a conservation area.

C Because it can be retro-fitted

Radio House in Cambridge is another building with a striking curved roof, this one comprising 11 barrel vaults. Tasked with upgrading the office block to prevent water ingress, roofing specialist Alumasc installed its advanced waterproofing system Derbigum. Applied on top of the existing membrane roof, the system eliminates the need to remove old material, saving on time, labour and disposal costs.

Approved installer Camflat Roofing first treated the existing membrane with Alumasc bitumen primer, followed by a layer of actual primer. Next, 100mm of 100% recyclable Korklite Plus insulating panels were positioned and lightly scored to enable the panels to flex around the curved radius of each vault. The panels were then fully bonded in Hi-Ten Universal bitumen, and finally the 4mm-thick Derbigum membrane was torch applied to provide a totally waterproof and UV-stabilised covering.

D Because it's low carbon and low cost

Sustainability and budget constraints were high on the agenda for Neil Sutherland Architects when designing the extension to this Forestry Commission building on Dingwall Business Park near Inverness.

Featuring a locally sourced, large section Douglas fir post and beam frame with highly insulated timber-frame external walls and biomass heating, the building is also roofed with Marley Eternit’s low-embodied energy fibre cement profiled sheeting.

The inward-sloping mono pitch roof rises from the existing eaves, creating an internal gutter between the old and new. This provides increased height at the new external wall, which has a glazed clerestory that runs the length of the building. The gun metal grey-profiled sheeting helped the roof blend in with the lead used on the extension’s celestory. ‘It also enabled us to meet the brief in terms of budget and sustainability,’ said Colin Henderson, architect partner at Neil Sutherland Architects.

E Because you want perfect pitch

The new 10,000-seater rugby and football stadium at Leigh Sports Village is one of several venues being constructed to host Olympians training in the run-up to the London 2012 games. To protect spectators from the elements, as well as allow natural daylight to reach the pitch, architect Insight Technical Services specified over 3,600m² of Brett Martin’s Trilite Ultra 45 translucent GRP sheeting for the stadium’s canopy roof.

The tinted profiled sheet canopy extends the aluminium standing seam roof across the pitch, and is supplemented by 500m² of tinted profiled sheet underneath the terraces to complement the louvered external walls of the concourse.

The company says the 4.5kg/m² GRP sheet can handle the loads typical of inadvertent foot traffic or a falling person. It was also used as vertical cladding to increase natural light underneath terraces and to minimise artificial light requirements during the day.