General Green Roof Types for Small Green Roofs
The type of vegetation for a green roof can be loosely classified in these categories:
Lightweight Extensive Green Roof – using sedum blanket or mat solutions – below 90kg/m2
Sedum plant species are well adapted for use on extensive and semi-extensive green roofs. The species are very drought tolerant, normally able to withstand climate extremes and, because of this, are regularly grown in or on shallow substrate layers.
- There are solutions that are marketed that can be installed with a saturated weight of only 55kg/m2
- We would always recommend that, wherever possible, you try to install with at least 80mm of substrate (preferably more) – with the blanket or mat this would give you a saturated weight of approximately 120kg/m2
- Sedums are very low maintenance.
Extensive Green Roof – sedum and herb roofs using seeds plug plants and or turfs/blankets
Biodiverse roofs are created primarily for biodiversity purposes and can aim to create or enhance habitats for insects, birds, plants and animals. This includes what is known as the “Brown Roof”, which is not purposefully planted but instead the growing medium is chosen and installed and then left untended to allow indigenous plant species to naturally colonise the roof over time.
- This is the approach we recommend where circumstances allow – depending on the depth of substrate the saturated weight would between 120 – 250kg/m2
- generally low maintenance, but may need some irrigation during extended periods of drought. The Guide includes instruction on building in an irrigation system that you may wish to consider at the planning stage.
Semi-intensive Green Roof – herbs, food, ornamental flowers
These are the more classic garden type green roofs which will require a higher roof loading and considerably more maintenance to keep in good condition.
- Generally an semi-intensive green roof needs regular maintenance – saturated weight of between 170 – 300kg/m2
- medium maintenance with regular irrigation through dry periods.
