Green Roofing Directive - what does it say?

The term "green roof" often comes up once, but hardly anyone knows what this directive says and by whom it is created. This article closes these gaps in knowledge.

The green roofs directive

The Forschungsgesellschaft Landschaftsentwicklung und Landschaftsbau e.V., also known as FLL for short, is a Bonn-based registered association that has been dealing with questions of landscaping and landscape development on a scientific level since 1975.

The FLL also passes the so-called Green Roofing Directive, which deals with all aspects of green roofs, with the right and optimal structure, the care as well as the correct planning of green roofs.

The green roofs guideline of the FLL is regarded by all experts as practically binding, even the DIN refers in many cases to the guideline. If you want to green your roof, you can not get around the guidelines of the directive.

Especially, as far as the correct roof construction is concerned, you should absolutely adhere to the specifications.

The individual layers in the roof structure after the FLL (from bottom to top)

  • separating layer
  • protective layer
  • Durchwurzelungsschicht
  • drainage layer
  • filter layer
  • Vegetation layer (in extensive greening mostly two-layered)

Additional relevant guidelines

In addition to the requirements mentioned in the DIN, there is an important guideline regarding green roofs.

These are the so-called flat message lines, more precisely the "guidelines for the design and execution of roofs with waterproofing" of the Central Association of Roofing Trade. Here, too, reference is made to green roofs and the necessary conditions.

For the planning of a green roof, you should always include an experienced roofing company, because both the high possible roof loads, which can sometimes be well over 60 kg per square meter, make a professional assessment necessary in any case.

Tips & Tricks

Also, make sure that you can only apply extensive vegetation to some types of roofs and others may need additional drainage.

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