Green roofing on flat roofs - how to execute?

So, it's done now. Delivery was at 6:00 PM yesterday and by 12:00 PM today the green roof was finished: 34 m², 6 hours of work, 2 people. The result is convincing.

Before:



Delivery:



Root protection foil, drainage mats, substrate cassettes, gravel strip:



Finished:

Thank you for the great experience report. I am currently building as well and need to green about 75% of the roof, approximately 100 sqm. Do I need to consider a specific load-bearing capacity? Does the roof need to be prepared for this or can I simply build it on our flat roof, just like you? Thanks for a message.

Thank you for the great experience report. I am currently building as well and need to green about 75% of the roof, approximately 100 sqm. Do I need to pay special attention to the load-bearing capacity? Does the roof need to be prepared for this or can I simply build it on our flat roof like you did? Thanks for a message

Whether you can build directly on the existing roof depends on the waterproofing. It works with a membrane roof. With roofing felt, an additional membrane is needed. Regarding the load-bearing capacity, it helps to look at the structural calculations or call a structural engineer. The manufacturer reveals how much the green roof weighs per square meter. To that, you would add the rainwater that can be retained, which significantly increases the total weight. For my green roof, I assumed a maximum of 150 kg/m² in total. Since my roof has a concrete slab beneath the membrane and insulation, this was not a problem.

Per cm of substrate, you should calculate with a roof load of 10kg/sqm.