Roofs as we know them are unkind to the environment with their contribution to global warming from the use of clay and concrete tiles, slates, sheet metal etc., and the way rainwater is shed as quickly as possible away into the water courses contributing, amongst other things, to downstream flooding.
Green roofs do much to ameliorate these effects by reducing ambient temperatures and improved rainwater management. They also help in biodiversity, through habitat provision, are visually attractive and can be used as additional amenity space.
Roof gardens can replicate almost any ground design garden. In all cases:-
- The roof must be capable of supporting the design load
- There must be adequate provision to drain excess rainwater
- Safe access for maintenance must be included in the design
The roof waterproofing must:-
- Be robust
- Be long lasting
- Resist root action
- Have outlets capable of inspection
- Be laid with the highest standard of workmanship in accordance with the general principles of membrane design
There is no UK legislation demanding roof greening though local planning guidance may call for green roofs in some locations. However green roofs can considerably reduce rain water runoff and can be incorporated into sustainable urban drainage schemes (SUDS). Furthermore green roofs will, with certain conditions, automatically be awarded one credit under the Code for Sustainable Homes – Surface Water Management (SUR1).