When planning to construct a green roof, it is important to consider the potential future use of the green area, irrespective of whether a new building is being constructed or a new one renovated. There are three basic types of green roof systems. We differentiate between the following types of green roofs, depending on how the area is to be utilised, the technical parameters and requirements, and the form of construction (these also determine what plants and form of vegetation can be employed):
The various types of green roofs
ExtensiveExtensive systems represent the form closest to nature and are mainly laid down on roof areas that will not be used. As the possibilities for active maintenance are low due to poor accessibility, it is necessary to select appropriate vegetation.
Due to the extreme situation, the plants need to be low-maintenance, adaptable and self-sustaining; they also need to be resistant to drought and frost, while being able to survive occasional overirrigation and lack of nutrients.
IntensiveIn contrast with an extensive green roof, there are almost unlimited possibilities with respect to the plants that can be used in an intensive system. In view of the wide range of plants that can be employed, the resultant high level of maintenance required, and the fact that the space is regularly used, an extensive green roof is frequently indistinguishable from a garden or other accessible green space.
Standard green roof construction techniques
In the long tradition of green roof systems, a layered build-up of the vegetation surface has been most effective and this is now the standard procedure. Every layer needs to fulfil a specific function and must be appropriately adjusted to suit the requirements of the location and the vegetation employed.
The planting of a green roof
To ensure the success and long life of a green roof, it is important to select the right plants. As a green roof is an artificially planted area, the specific climatic conditions and other local factors, such as the urban microclimate, ratio of light and shade, wind exposure, pollutant exposure, exposure to heat and cold, roof orientation etc., must be taken into account together with the relevant parameters of the type of green roof to be constructed.
The plant groups that can be recommended for planting on green roofs are mosses, succulents, bulbs and tubers, grasses, herbs, herbaceous and woody plants. A few of the more popular and recommended plant combinations are listed below: