Introduction to types of green roofs on buildings in cities

Types of Green Roofs.

Intensive green roof garden - London
Intensive green roof garden – London

Green roofs are internationally placed in three different ‘types’: Of course there is some cross over between the categories.

The planning, implementation and maintenance of all these types is covered in the UK Green roof Code of Practice. known as the GRO code. All green roof codes of practice globally are based on the German FLL.

Types of green roofs - extensive
Extensive green roof – Camber, Sussex UK

 

Although extensive green roofs are perceived as using sedums and succulents, wildflowers can be used. This is an approach that is common in the UK and Switzerland.  In the UK there are three sub-categories:

  • Extensive sedum
  • Extensive biodiverse
  • Brown roofs

In the recent past, which Livingroofs.org was partly responsible for, brown roofs was a widely used term. Although some people still refer to old style brown roofs, they should be considered as extensive biodiverse roofs. They should also be designed and considered as ecological landscapes and not as a product.

A summary of the general characteristics of each category can be seen below. Although there is some cross over, the maintenance, costs and structural requirements do differ. Furthermore we have provided an overview of the broad benefits to the environment of each.

Table: General Features of the Green Roof

Type ➔ExtensiveSemi-intensiveIntensive
UseEcological LandscapeGarden/Ecological LandscapeGarden/Park
Type of vegetationMoss-Herbs-GrassesGrass-Herbs-ShrubsLawn/Perennials, Shrubs, Trees
BenefitW,T,BW,T,B,AW,T,B,A
Depth of Substrate60-200mm120-250mm150-400mm
Weight60-150 kg/m2120-200 kg/m2180-500 kg/m2
CostLowPeriodicHigh

W= Water, T= Thermal, B= Biodiversity, A= Amenity