A green roof is a sustainable addition to many roofs, but not every roof is automatically suitable. Whether greening is possible depends on a number of technical prerequisites that determine whether the roof can be made safe, sustainable and future-proof.

Bearing capacity of the roof

A green roof weighs more than a standard roofing material, especially when fully saturated with water. On average, a sedum roof weighs around sixty kilograms per square meter, while green roofs with herbs or a rooftop flower meadow can reach about ninety kilograms per square meter. For lighter structures, such as wooden roofs, lightweight construction is often chosen. When in doubt, it is wise to have a roof inspector check the load-bearing capacity beforehand. That way you can be sure that your roof structure can handle the weight of a green roof.

Water loading and drainage

The suitability of a roof involves not only the weight of the green roof, but also how the roof handles rainwater. A green roof captures rain and temporarily stores it in the substrate and vegetation. This means that when it rains, the roof is put under extra stress. The water is then released gradually, rather than flowing into the sewer system all at once.

Therefore, proper drainage is essential. Excess water should always be able to drain safely to prevent water accumulation on the roof. If drains, slope or details around eaves are not done properly, this can cause problems over time. A well-designed green roof combines water storage with reliable drainage to keep the roof functioning even during heavy rainfall.

Roofing as a basis

The existing roofing material forms the basis of a green roof and must therefore be suitable and in good condition. Bitumen and EPDM are both suitable substrates for a green roof, provided they are undamaged and properly installed. The benefits of a green roof include protecting the roof from UV radiation and temperature fluctuations.

Roof pitch and technical feasibility

Green roofs are often used on flat roofs, but sloping roofs are also suitable for greening. With a larger roof pitch, an appropriate structure is required to prevent shifting of substrate and vegetation. When technically taken into account, green roofs on sloping roofs function just as reliably as on flat roofs.

Conclusion: when is a roof suitable for a green roof?

A roof is suitable for a green roof when it can bear the extra weight, the roofing is in good condition and rainwater can be drained properly. In practice, many roofs can be made suitable with the right choices. By looking carefully at the technical principles in advance, you can avoid problems and enjoy a safe, durable and low-maintenance green roof for years to come.