A composite buildup for a circulair and optionally biobased green roof based on expanded cork. Cork is extracted from the bark of the cork oak in Portugal. The residuals from the production of winebottle cork is ground into granules. These granules are in special steam ovens pressed into expanded cork blocks without additional additives. The blocks are then cut into boards of different thickness.

The expanded cork gives the green roof drainage and provides extra insulation. On top of the cork is a layer of cloth made from recycled synthetic clothing fibers and a substrate from recycled roof tiles.