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.

Extensive Dachbegrünung für steile Dächer - TOPGREEN-Gründachsysteme

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°.


Roof structure

The smaller green roof build-up for extensive green roofs represents significantly lighter loads for roofs than intensive green roofing. The weight of a green roofing build-up is approximately 120 kg/m² and has a depth of approximately 8 centimetres (when realised using a TOPGREEN green roofing system). What may seem a lot at first glance is, at second glance, already present on many flat roofs. Existing flat roofs have often already been provided with a gravel infill, which places a load of approximately 90 kg/m² to 150 kg/m² on the roof. This means that in many cases there are no difficulties in changing to extensive green roofing, especially on flat roofs. In addition to the roof load, the root protection present is also an important prerequisite. If your roof seal or waterproofing does not comply with German FLL guidelines, you must apply additional root protection in the form of a root protection foil. This will ensures that your roof is protected against root growth.

Important: As one of the most important prerequisites for green roofing, you should always play it , when checking the roof loading, and consult a roofer or structural engineer. Also clarify with the roofer, whether your root protection meets requirements of FLL guidelines.

Extensive Dachbegrünung - Dachkonstruktion - TOPGREEN-Gründachsysteme

Roof pitches

Implementation of green roofing is possible on flat roofs as well as on pitched and steep roofs. Intensive green roofing is usually only implemented on flat and slightly inclined roofs, whereas extensive green roofs can be used on steep roofs inclined up to 45°. Almost every roof is different and therefore the requirements for green roofing also differ with each project. Even during the design phase of your roof, consider green roofing, in order to avoid difficulties that may arise later. To ensure that water which plants cannot absorb will run off, a roofing pitch of at least 1 degree must be maintained.

Extensivbegrünung - Dachneigung - TOPGREEN-Gründachsysteme

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:

Extensiv begrüntes Flachdach mit Sedumsprossen - TOPGREEN-Gründachsyteme

Greening using sedum sprouts

When fitting plants for extensive greening, we distinguish between two different variants. With sedum sprouts, we are dealing with live shoots of individual sedum plants. These plant parts are simply distributed evenly over the entire roof surface covering. They can be applied directly to the substrate layer and thus form the finishing touches for the green roofing structure. After installing sedum sprouts, they must be lightly pressed down or raked in so that they can optimally connect to the substrate layer. Sedum shoots are delivered to you in an air-permeable bag and should be processed within 48 hours of delivery, if possible.

Important: After installing sedum shoots on your roof, regular watering during the first 4-6 weeks is an absolute requirement. Pay attention to the moisture level of soil and re-water depending on the weather. This is the only way for the shoots to take root sufficiently and to form an even and closed covering of plants. Please feel free to contact us with any questions on planting sedum shoots - we will be only to happy to help.

Sedummatten für die extensive Dachbegrünung - TOPGREEN-Gründachsysteme

Pre-cultivated sedum matting

You can achieve a green roof very quickly and conveniently using pre-cultivated sedum mats. Sedum mats are supplied with almost fully grown plants. The mats usually consist of 5-6 different species of plants, already taking root in a substrate layer. There is a carrier layer of fleece or coconut fabric beneath this substrate layer. Sedum mats are laid onto the existing substrate of the green roof in a similar way to rolled turf. In order to ensure optimal growth of plants on sedum mats, the substrate layer beneath it should be not less than approx. 5 cm thick. This is the only way to achieve a long-life green roof.

The individual mats are then laid on the roof substrate almost seamlessly alongside one other, and the roof becomes green immediately – with no lengthy waiting times. This type of planting can be used for both flat and pitched green roofs. Sedum matting is especially well-suited to extensive greening of pitched roofs and can be processed quickly and easily.

Further information on green roofs

Benefits of green roofs

Green roofs - not just an attractive appearance, but also characterised by numerous environmental advantages. Learn more about the many advantages of green roofs.

Plant list

The list of plants suitable for green roofing is longer than you might at first expect. We have summarised some interesting aspects for you.

Flat green roofs

Flat green roofs make an important contribution to climate protection and deliver a variety of benefits. Learn more from this overview.