Greening a tiled roof requires special treatment. A green roof cannot be installed directly on a tiled roof. If the building has adequate load capacity, or if structural reinforcement and a support system can be incorporated into the design, a green roof may be constructed as a self-contained waterproof module that sits above the existing roof. Drainage from the green roof must connect directly into the lower level roof drainage system. It may be more economical to replace the roof to make it suitable for a green roof.
The components installed on the roof deck will be either loose-laid over the roof surface or installed as modules that connect together to form a continuous effect. Individual containers that are separately placed on a roof deck are considered a roof garden rather than a green roof, and because they do not cover a significant proportion of the roof they do not provide most of the benefits associated with green roofs.
It may be necessary to remove or relocate existing infrastructure on roof decks, or the green roof can be built around the equipment.