One Green roof can double the durability of the roof
Green roofs as roof coverings of the future are actually no longer a romantic daydream, because nature is on the way to return to the city. They increase the quality of our living space, allow rainwater to evaporate better and also have a positive influence on climatic conditions. Green roofs cool the houses in summer, insulate them in winter and their construction is even financially supported. The garden journal has just published a detailed article on the technical and organizational details of green roofs. And yet, most homeowners are still skeptical.
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Against all prejudices: green roofs as a small project
The most common objections made by property owners include fears that a green roof could be damaged by the Plantings could be damaged and such projects too expensive and too complex in terms of design would be. Ergo: Just try the extensive greening of the tool shed, the dog house or the bird house! And as far as the reduced durability of house roofs is concerned, the Association of German Roof Gardeners knows. V. Anyway, better and more specifically verifiable analytically: "The durability of a (bare) flat roof is only 15 - 25 years on average, even with a professional design" *. And: "Numerous green roofs from the 1970s prove that properly executed green roofs can easily double the service life of the waterproofing". *
Extensive green roofs: not just easy to maintain
Green roofs blend in well with the landscape
This method of a total of three types of greening for roofs is also optimal in terms of static load-bearing capacity, especially for light roof constructions. In addition, extensive greening usually does not require any additional irrigation. Almost all professionally sealed roof structures (flat, saddle, monopitch or barrel roof) are suitable for greening, provided that the structural specifications are taken into account. For roofs without a slope, drainage elements that bind moisture must also be provided so that the plants can also use extensive Rainfall take no damage.
Careful planning - the essentials for green roofs
Careful design planning is not only decisive for the subsequent maintenance effort and the expected costs, but also has optical effects that one must be aware of before the first wheelbarrows with gravel, substrate and perennials are hoisted onto the roof of the house will. So:
- Define framework conditions: type of substrate material, required structure thickness, plan options for tanning;
- Selection of the planned planting material: taking into account the natural mutual competition or Sociability, expected growth forms and the time of flowering taking into account species protection;
- Creation of a planting plan: Fixing the desired locations with the number of plants as well as the selection of the optimal planting method.
If you are unsure of yourself, do not be afraid to seek professional advice on any questions and problems that may arise. On the portal of the German Roof Gardeners Association e. V. you will find up-to-date address material from experienced roof gardeners in your region as well as relevant specialist dealers, manufacturers and associations who support and accompany your green roof project.
Planting options for extensive green roofs
Not all plants are suitable for green roofs
Undemanding and drought-resistant plants that get by with a relatively thin and therefore light substrate layer are particularly suitable for this. Roof slopes between 2 and a maximum of 15 percent, which can withstand a total weight of around 120 kg per square meter of roof area, are ideal. Plants with roots that are as small and flat as possible or pre-cultivated plant mats are ideal. In addition, there is also the green roof out of the bag. It contains, in addition to low-maintenance, rough meadow plants, mostly different Sedum and Sempervivum species that are suitable for the sowing on a three to four square meter roof area are sufficient. Here are a few more planting ideas from the DDV in short tabular form:
| Botanical name | German name | Flower color and flowering time | Height (cm) | Note |
|---|---|---|---|---|
| Sedum album | White stonecrop | white-pink, VI to VIII | 5 to 10 | forms loose lawns, different leaf colors (green, red, brown) |
| China Sedum | Sedum plant | golden yellow, VI to VII | 10 to 15 | Carpet maker, also partial shade |
| Sedum hybridum "evergreen" | Mongol Sedum | golden yellow, VII to VIII | 10 to 15 | Forming dense, evergreen mats, also partial shade |
| Sedum reflexum | Tripmadam | golden yellow, VII | 15 to 30 | Forming loose lawns, old aromatic plant |
| Sedum sexangulare | Mild stonecrop | yellow, VI to VII | 5 to 10 | Dense mats and pads |
| Sedum spurium various sorts | Carpet Sedum | pink, white, carmine, VII to VIII | 5 to 15 | Carpet maker, very vigorous and dense, also partial shade |
| Dianthus carthusianorum | Carthusian carnation | purple red, VI to IX | 20 to 40 | loose grass growth, self-sowing |
| Dianthus deltoides | Heather carnation | pink, VI to IX | 5 to 15 | lawn-like, green-brown-green cushions |
| Dianthus plumarius | Feather carnation | white, pink, red, V to VI | 10 to 30 | densely grassed cushions, strongly scented |
| Hieracium pilosella | Small hawkweed, mouse ears | yellow, V to IX | 5 to 10 | loose, grass-like growth |
| Koeleriaglauca | Schillergrass | blue green | 20 to 30 | broad-leaved clumps |
| Petrorhagia saxifraga | Stone carnation | white-pink, VI to IX | 10 to 20 | loose, fragrant veils of flowers |
| Saponaria ocymoides | Upholstery soapwort | pink, VI to VII | 15 to 20 | Undemanding upholstered shrub |
| Sempervivum hybrids | Roof root, houseleek | different colors, shapes and sizes, VII to IX | 5 to 30 | Mat and carpet maker |
| Thymus serpyllum | Creeping thyme | purple-pink, V to VIII | 3 to 5 | overgrown, fragrant, different varieties |
Source: Deutscher Dachgärtner Verband e. V.
Finally, pour all or part of it briefly and lean back comfortably, because the work is done. You will hardly have to worry about the new green roof in the future and, above all, hold back on watering. This would only fuel the settlement and spread of undesirable weeds. From time to time it is only necessary to remove the spreading seedlings from the roof, there is not much more to do.
* Quote from: DDV practical guide "The 1 x 1 of green roofs" from German Roof Gardeners Association V., Nürtingen, 2016.
