There are potential savings for developers and owners in that a green roof installation could reduce the number of drainage outlets.

A number of developers and green roof manufacturers have pointed out that quantity surveyors are unlikely to factor in these cost benefits, as they tend to separate the costs of roofs and drainage. However, depending on the size of the roof and the height of the building, the cost benefit of drainage outlet savings could significantly offset the cost of a green roof.

Industrial buildings, if designed at the planning stage, can take the weight of a green roof. The additional cost of a strengthening deck is outweighed by the reduction in drainage capacity requirement both on the roof and at ground level.