Green roofing Sauna & Garden house

Hello, we each have 3*4 wooden saunas and wooden garden houses outdoors. There is a slight slope on the roof and a special membrane has been laid. Now we want to address the topic of green roofing.

The sauna builder says a maximum of 250-300kg per roof is allowed to guarantee stability.

What options are there for "light" green roofing? Currently, a puddle always remains on the roof and does not drain.

Are there also light stones that absorb water and allow it to evaporate?

I look forward to suggestions.

Are we talking about 250kg per square meter or 250kg total? If the former, I see no leeway. That would be 20kg/sqm.

And what about the puddle? How big is it and shouldn't it drain with a properly executed slope?

Are we talking about 250kg per square meter or 250kg total? If the former, I see no room for maneuver. That would then be 20kg/sqm

And what about the puddle? How big is it and shouldn’t it drain with a properly executed slope?

A total of 250 kg ………….. so there is no lightweight material?

The problem is not just the material. You also want to absorb water. That further reduces the weight you can bring onto the roof.

How is it actually with the snow load on the roof? How is that already factored in?

The problem is not just the material. You also want to carry water. That further reduces the weight you can put on the roof. How is the snow load actually calculated on the roof? How is that already taken into account?

Good question. But we hardly have any snow in our region. And if some comes, it melts away.

I just thought that too, snow load, rainwater added, one person to shovel up there. The sauna builder, or you yourself, should insert a few more beams and increase the slope. Flat roofs of saunas or sheds become leaky if puddles stand on them