Types of Greenroofs

There are two main types of greenroofs - extensive or intensive - although a greenroof is often designed with features of both and then is referred to as either semi-extensive or semi-intensive. Commonly, the roof function or objective of the roof space determines the design - is it just an ecological cover or is it intended for human recreation, vegetable gardening, etc.?

Extensive (eco-roofs or low-profile) These have thinner and less numbers of layers, so therefore they are lighter, less expensive and very low maintenance. They are built when the primary desire is for an ecological roof cover with limited human access

Minimum growing media/soil substrate - 8î-12î Media composition: 50 ñ 55% inorganic to 45 ñ 50% organic Architectural features like gazebos & benches plus plant heights of up to 15ft.

Intensive (high-profile) These look like traditional roof gardens because a much wider variety of plant material can be included since growing media depths are increased. Architectural accents such as waterfalls, ponds, gazebos, etc. are possible and these greenroofs provide recreation spaces and encourage interaction between people and nature. Maintenance requirements are also more intensive and these roofs are relatively flat.

Minimum growing media/soil substrate - 2.5î - 6î
Media composition: 70 ñ 80% inorganic to 20 ñ 30% organic
Low growing, horizontally spreading plant heights of 16"-24î

Differences in Meanings These two terms are now used interchangeably and are gradually losing their original definitions:

Intensive Greenroof - indicates there is a drainage system fitted with plants directly embedded in the soil.

Roof Garden - all plants are kept in containers sitting on a hard roof surface and are easily removable.