Extensive roofs serve as an ecological covering that provides society with environmental benefits and the building owner with life cycle cost benefits. A lightweight, low-maintenance roof system, typically with sedum or a wild flower mix planted into a shallow growing substrate usually no more than 100mm that is low in nutrients. Irrigation is not normally required.

Extensive roofs are composed of lightweight layers of free-draining material that support low-growing, hardy vegetation. They are often used on garden structure like sheds and garages as they are lightweight, they require little or no additional structural support from the building. Furthermore, because the vegetation is adapted to the extreme roof top environment (high winds, hot sun, drought, and winter cold), extensive green roofs require little in the way of maintenance and resource inputs. Extensive green roofs can be designed into new buildings, or retrofitted onto existing buildings.

Hybrid Semi-Intensive

Hybrid (also known as Semi-Intensive) roof can include characteristics of both Extensive and Biodiverse roofs. Typically requiring a deeper level of substrate, a wider range of plants can be included such as shrubs and woody plants. Irrigation and maintenance requirements are dependent on the plants chosen.


Commonly known as a roof garden due to the fact that its appearance is like that of a regular garden. Quite often they incorporate pathways and seating areas. Intensive roofs are predominately used for recreation and require regular maintenance and irrigation as you would in any garden. They require a relatively deep substrate of at least 200mm but can range up to over a metre and can therefore support a wide range of plant types including trees, shrubs and grasses – lesser substrate thickness is required for a simpler covering of lawn or ground covering vegetation.

They are generally heavy and normally require a concrete substrate to support the extra loading requirement. Because intensive green roofs need the same level of upkeep as a regular garden, access is essential and irrigation systems are often required to aid maintenance.


A brown roof is similar in composition to an extensive roof, but is designed specifically to create a habitat that will attract a particular plant and animal by replicating the original footprint of the building or enhancing the previous habitat. A brown roof can be non-vegetated. The growing medium is purposely selected to allow native plant species to inhabit the roof over time. The growing media can be mixed with recycled aggregate from site and generally left to colonize naturally or seeded with an annual wildflower mix or local seed source.

When considering a bio diverse roof it is important to ensure the quality of the aggregate has a sufficient capacity to hold rainwater. On commercial projects it is important that contractors avoid dumping waste material on the roof. Recent research and experience suggests the use of commercial crushed brick or other porous type substrate to ensure quality and known water storage. This type of roof will need higher organic content to ensure that the seeds and wildflower can flourish.

Please contact us to arrange a meeting to discuss your specific requirements at your convenience.

atal uk are able to aid design, supply and install if required.