ᐅ Green Roof for Sauna and Garden Shed

Hello, we have two wooden buildings outdoors: a 3 x 4 meter (10 x 13 feet) sauna and a wooden garden shed. The roofs have a slight slope, and a special membrane has been installed. Now we want to start working on green roofing.

The sauna builder says that each roof can support a maximum of 250–300 kg (550–660 lbs) to guarantee stability.

What options are there for “lightweight” green roofs? Currently, water always pools on the roof and does not drain away.

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

I look forward to your suggestions.

Are we talking about 250 kg per square meter or 250 kg total? If it’s the former, I don’t see any leeway. That would mean 20 kg/sqm (4 lb/sq ft).

And what about the puddle? How large is it, and shouldn’t it drain properly if the slope is correctly executed?

WilderSueden schrieb:

Are we talking about 250 kg per square meter or 250 kg total? If it’s the former, I don’t see any leeway. That would be 20 kg/sqm (4 lbs/sq ft).

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

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

The problem isn’t just the material. You also want to consider water absorption. That further reduces the weight you can put on the roof.

How is the snow load on the roof handled? How is that accounted for?

WilderSueden schrieb:

The problem isn’t just the material. You also want it to absorb water. That further reduces the weight you can put on the roof.

How is the snow load considered for the roof? How is that factored in there?

Good question. But in our area, we hardly get any snow. And when it does come, it melts away.

I was just thinking the same thing,
snow load, rainwater on top, and a person shoveling it off.
The sauna builder, or you yourself, should add some additional beams and increase the slope.
Flat roofs on saunas or sheds tend to leak if water pools remain on them.