Extensive green roofs - how is it structured?

For a green roof, of course, a corresponding roof structure must also be made. This also applies to extensive green roofs. This article explains how such a roof has to be constructed.

Protection for the roof must be provided

Extensive green roofs are more common than intensive ones in our latitudes - more than 80% of all green roofs are greened extensively.

  • Also read - The extensive greening for the roof
  • Also read - Extensive green roofs - Costs for the green eco-hood
  • Also read - The structure of the green roof

The difference between extensive and intensive greening lies in the structure of the ground - with extensive greening, the roof structure can therefore also be laid out much more simply.

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

Roofs with thermal insulation on top may need an additional drainage layer. With regard to the load-bearing capacity, coordination often has to take place.

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

  • Separating layer
  • Protective layer
  • Rooting layer
  • Drainage layer
  • Filter layer
  • Vegetation layer (with extensive greening usually two layers)

Area loads from green roofs

Extensive green roofs are significantly lighter than intensive ones, but the substrate and the individual layers still generate surface loads of between 40 and 60 kg per square meter of roof area.

These area loads must be able to be carried by the respective roof - where this is not the case, greening is usually not possible. The individual layers, as indicated above, can in no way be dispensed with.

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

Tips & Tricks The roof structure for a green roof should definitely be planned by an experienced specialist, as this can also result in possible damage to the roof due to planning errors.