Wherever possible, designers should ensure that roof penetrations for equipment, such as pipes and skylights, are concentrated together, as this will allow more unbroken planted areas. In addition, proper waterproofing principles must be ncorporated into a vegetated roof's design. Flashings should be terminated a minimum of 8 inches above the finished growing media surface or top of pavers.

The 8,800 sq.ft Extensive Garden Roof on Philadelphia Water Department Maintenance Facility is a great example!