Extensive green roofs basically require very little servicing. The special properties of plants are reflected in the minimum servicing required. As a rule, only one or two service visits are required every year. The specific servicing and maintenance work varies depending on the location and scope of the green roof.
Annually, woody plants and shrubs which are present (such as birch, willows) and herbs (such as clover, dandelions, vetches, etc.) must be removed, preferably including the roots and before sowing. Remove the plants from the roof.
Removing unwanted plants and shrubbery applies not only to the actual green roofing area, but also to strips of gravel ballast, paths, walkways and adjacent terraces.
As a rule, a slow-release fertiliser containing 5 g of pure nitrogen should be applied evenly to the green roofing area once a year in spring (April/May). Especially strong moss growth or conspicuously red-coloured sedum species may be signs of a nutrient deficiency.
Inspection shafts and roof drains below them must be inspected annually and cleaned of contaminants (anthills, dirt, leaves, lime deposits, etc.). The cross-section of the drain must not be changed. The above also applies to drainage channels and gutters.
As a rule, extensive green roofs are no longer watered after end-of-build servicing, i.e. once well over half the area has been covered and is over one year old. Even during hot, dry summers, irrigating with water is usually not necessary. Exceptions could be: a very thin-layer of greenery less than 7 cm thick and south facing steep roofs, with less than 10 cm thick coverings.
If areas (approx. greater than 0.5 m²) are not covered with vegetation or erosion has occurred in certain places, it may be necessary to refill green roofing substrate and plants suitable as low-growing perennials or scattering seeds + sedum shoots. The appropriate time for this is in April/May and possibly in September/October too.
