The turf will top a Southern Water treatment centre on the South Downs in an £800,000 project. Frosts Landscapes Construction starts the 16,000sq m job this month and expects it to take a year. The turf will lie on a 200mm substrate of topsoil, crushed brick and concrete.
"The roof has a gradient of 15 degrees and sweeps into the surrounding profile of the South Downs," said landscape construction director Aidan Lane. "We won the job because of our emphasis on horticulture and trialled seven different substrates for the turf."
He added that a few other roof gardens, such as the one commissioned by Rolls-Royce, were bigger but this project had a thick substrate and totalled 3,500cu m of material. Local topsoil may also be blended into the mix to encourage the area's rare green-winged orchid to establish itself among the turf.
"We do quite a lot of roof gardens but this one for Southern Water is a good one to have on the books," said Lane, who is also handling several jobs for the Olympics.
The company is also tackling green-roofed podiums, soft landscape, granite paving and lighting in a £1.7m job on London's South Bank, while Parkway, a new shopping centre in Newbury, will include podium turf, five roof gardens, drainage and irrigation in a job worth £3m.