Extensive green roofs – a type of green roof with low service and maintenance requirements

Extensive green roofing is a type of green roof that can be implemented with a simple build-up and low service and maintenance requirements. Extensive green roofs are especially suitable for green roof areas not permanently in use, and which are only walked on during any service or maintenance work.

Smaller areas on garages, carports, garden sheds or even bin stores are also wonderfully suited to providing a green paradise. The choice of plants takes into account that the plants (moss, grass, wild herbs and succulents) are able to thrive and prosper independently, with no need for or only low servicing requirements. This type of green roofing corresponds to near-natural vegetation, which not only has visual but also numerous environmental benefits.

Intensive or extensive green roofing

A fundamental distinction is made between intensive and extensive green roofing. Intensive green roofs are clearly the more elaborate variety. Intensive green roofs can also be aptly described using the term "roof gardens". This type is usually only implemented on flat or slightly inclined roofs (up to 5° roof pitch). The costs of intensive greening roof depend on the scope of the project, and may vary greatly depending on the project. Basically, however, costs are significantly higher than those for extensive green roofs. Likewise, servicing and maintenance work and requirements for intensive green roofs are comparable to that of a normal garden, and thus significantly higher than that for extensive green roofs.

In addition, the additional weight of the increased green roofing build-up must be taken into account during design stages of the roof build-up – precisely with existing flat roofs, this is usually not taken into account in static engineering terms. The plants used also place higher demands on the build-up and on the need for regular watering and supply of nutrients. Nevertheless, intensive green roofs are especially suitable in urban regions where available living space and green spaces on hand are limited. By creating these large green spaces, new usable spaces are created and areas that were previously embellished by roofing felt can blossom and may be used.

With extensive green roofs, on the other hand, you will benefit especially from the low-maintenance requirements and simple build-up of the green roof. The thin build-up layer of an extensive green roof is lighter than that for intensive green roofs, and this form of green roof can be created more quickly. When selecting the plants, it is important to ensure that they are not sensitive to frost and droughts or dryness and that they only require a small amount of nutrients. Species of sedum selected have proven to be particularly suitable. These can be meaningfully supplemented by other species of plants, so that natural or near-natural greening can be created. Extensive green roofing provides observers with a beautiful view all year round, influenced to a large part by nature. Skilful planning can further minimise servicing requirements. For example, there should be a small strip with no plants present at existing skylights or roof-lights.

What to take into account with extensive green roofs?

If you wish to install extensive green roofing on your roof, there are some prerequisites that you should take into account, as early as the design phase of your roof. You must definitely observe important prerequisites even for existing roof surfaces, which you wish to supplement with a green roof. Extensive green roofing is suitable for flat roofs (minimum 1° roof angle of inclination or pitch) as well as for pitched roofs with a pitches of up to 45°.

What plants are suitable for extensive greening?

Different plants with low growth heights are suitable for extensive greening. Species such as mosses, sedums, grasses and herbs are particularly suitable. These plants can withstand the extreme conditions of the "roof" habitat and have all the necessary properties for green roofing. They have the capacity to be highly regenerative and can therefore get by with a lower supply of water and nutrients. Species which perform better in the shade or are susceptible in wind breaks are not suitable for extensive greening. Thanks to the different plant species, the observers of green roofs will be provided a versatile and beautiful image with different plants growing to different heights and with different colours of flowers. A variety of planting options are available:

Further information on green roofs