A garden on the roof convinces not only with its appearance, but is also an interesting component of ecological construction. This is because a green roof of plants and shrubs creates significant biotopes and improves air quality. In addition, temperature changes in summer and winter are balanced: In summer, the green roof cools and in winter it keeps warm. Green roofing also extends the longevity of the roof by, for example, partially retaining rain from the roof. But to build a thriving and well-functioning green roof, some important aspects must be considered.
In order to protect the components on the roof that lie under the greenery from the effects of the weather, it is important to lay out a roof membrane as well as root protection. This is necessary to drain rainwater and protect the roof from drifting plant roots. Special films with a polyolefin-coated fabric are more suitable for the plant protection layer than PVC films, as they are ecologically harmless. Also, the topsoil must be supplied with important nutrients and mineral light aggregates. If the roof does not have a drainage layer, make sure that the amount of topsoil is higher at the top than at the bottom. This has the effect of increasing the drainage effect of the substrate at the bottom of the roof.
If the topsoil is very rich in nutrients, it should be leached with the addition of sand. Depending on the roof slope and vegetation, different substrate thicknesses are recommended. If a roof has a slope of more than 5 percent and is characterized by extensive greening, the substrate thickness should be 15 centimeters. To prevent the plants from drying out, value should be placed on vegetation that is as dense as possible. If only a substrate thickness of 3 to 8 centimeters is permitted for structural reasons, mosses and sedum species are well suited for planting. A mixture of wild grasses and herbs goes well with a substrate thickness of between 12 and 15 centimeters.
Source: Ecological building
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