Extensive roof greening - how is it structured?

For a green roof, of course, a corresponding roof structure must be made. This also applies to extensive green roofs. How such a roof must be built up, you will find in this article explained.

Protection for the roof must be given

Extensive roof greening is more common in our latitudes than intensive - more than 80% of all green roofs are extensively landscaped.

The difference between extensive and intensive greening is in the soil structure - with extensive greening, the roof structure can therefore be much easier to create.

However, a prerequisite is the right type of roof, which may require special adjustments to the vegetation and the roof structure. This is the case, for example, with cold roofs.

Roofs with overhead thermal insulation may need an additional drainage layer. In terms of carrying capacity, often a vote must be made.

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

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

Area loads through green roofs

Although extensive green roofs are much lighter than intensive ones, they still generate surface loads of between 40 and 60 kg per square meter of roof area due to the substrate and the individual layers.

These area loads must be able to be removed from the respective roof - where this is not the case, a greening is usually not possible. On the individual layers, as stated above, can be waived under any circumstances.

Weight-determining is often the type of protective layer that is applied - for light loads geotextiles, such as certain nonwovens, are sufficient for heavier loads but concrete slabs or mastic asphalt are used here, which results in a corresponding weight load on the roof.

Tips & Tricks

The roof structure for a greening should be planned in any case by an experienced professional, since here also possible damage to the roof by planning errors can be the result.

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