Comment by pastage
7 days ago
Tradition says that this is not true but honestly I have no real experience except I have done the calculation for our roof. According to our local building standards at 60⁰ you basically have zero snow load, I am not sure what angle a shallow angle roof is but 30⁰ is max load. 6kN/m² is a lot of extra strength.
In Finland, where you can easily get 30cm or more snow, all roofs are required to stand 100-300kg/m2 by law and most roofs are less than 30 degrees (e.g. 1:2 ratio).
A-frame or even 45degree angle roofs are very rare.
30cm is just kinda cute. Try 600cm - you'll find a lot of A-frames up the mountain, where they routinely get >700cm of snow each year and generally no thaw until spring. Alaska, similarly, but there you'll find more domes and steep-roofed chalets, since it gets proper cold (-40) and insulation uber alles is the rule.
The other benefit of an A-frame is that the snow drifts deeply enough that winter-only cabins don't need as much insulation, because there's a 4m drift on all sides except the front.
Those kinds of places are also where you find "doors to nowhere" on the 2nd floor, because that's the winter access. One door at ground level for summer, one door ~1.5-2m up for winter.
I love visiting, but I'll never live there!
I read this as in Finland you can get 30cm snow in a day. And the second person is comparing that to 600cm in a year. Am I right?
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The only limit to how strong you can make a roof is really money. If you space joists or trusses half as far apart you will about double the max snow load.
At a certain point the problem stops being the roof, and starts being subsidence of the ground under the increasingly-heavy building.
That would be a LOT of snow.
With 60⁰ there is no snow accumulation at all but 35⁰-45⁰ pith roof will not hold all snow either. After it will accumulate some amount of snow (depending on the weather and an exact pith but rarely more than 50cm) snow will start to slide down.