Plants on extensive roof gardens should be able to survive and grow in high temperatures, full sun, high wind speeds and periods of drought. These should be able to survive in a thin substrate layer, a small waterbuffer and fluctuating temperatures.
An intensive roof garden provides plants with more soil, water and fertiliser availability. Selection factors for plants include the height of the roof, wind speeds, irrigation availability, sun position, relation to other buildings, climate zone
Create green roofs on new and existing buildings and fulfil the need for green where space is limited in the urban environment.
|Depth of soil||7-10 cm||for sedum, moss|
|25 cm||for shrubs|
|80 cm||for trees (0.75m per m canopy)|
|Weight||30-130 kg||for 2-15 cm soil|
|130 -300 kg||for 15-20 cm soil|
|250-1000 kg||for 15-80 cm soil|
|Maintenance||A conventional roof requires inspection 1 x per 5 years|
|An extensive green roof requires inspection 1x per year and weeding (no irrigation required)|
|An intensive green roof requires inspection 8 x per year (weeding, pruning and fertilizing) and always requires irrigation in dry periods.|
…The price of a garden is the same on the ground as on a roof: the land is already paid for! The extra costs of the roof construction/preparation, special soil mixture preparation and transportation of the materials to the roof make up the difference… Niek Roozen, landscape architect
In new & existing development:
Check local building codes and permits and have a structural engineer check the plans to be sure the roof is strong enough to hold the weight. It is also wise to compartmentalize the roof so it is easier to find the sources of possible leaks and prevent damage to neighbouring roofs.
In existing development:
The existing roof must be in good condition, strong enough, insulated and waterproof. Check if the insulating layer is under the waterproofing layer or over it and design accordingly. A layer of root barrier is also needed.
Pyrus salicifolia ‘Pendula’
Pinus nigra ‘Nigra’
Betula utilis ‘Doorenbos’