Frosts Landscape Construction rolled out 18,000sq m of turf on top of Southern Water's wastewater treatment works. The roof cost around £750,000 to build.
Frosts director Aidan Lane trialled grasses and substrates before choosing five seed mixes including Briza media and Cynosurus cristatus. Spearhead Turf, based in Cambridgeshire, supplied grass laid on loam, green waste and broken bricks.
"The substrate was 200mm deep and I wouldn't have thought that there are many roofs that compare," said Lane. "Most are around 65mm deep and this must be one of the biggest of its kind in Europe."