Comment by boringg
7 days ago
Depends what you are optimizing for -- roof collapse in a high snow load local or the level of efficiency for thermal properties. You can drive for high efficiency of your thermal properties but when your roof collapses those efficiencies are meaningless.
Home design is a game of engineering tradeoffs with the occasional new technology to improve things or lower costs.
An A-frame is a overkill solution to snow load when you can just make a shallower roof stronger.
only to a limit
enough snow, especially if compacted, especially if it involves melting + refreezing cycles turning part of it too ice and even robust concrete building can have some surprising issues
but it's true that for what most places in the world need a slightly tilted and structural stable roof is good enough, if you know how to clean it if things to south
If you get that much snow you should build heating into the roof to melt the snow just enough to slide off
2 replies →
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.
5 replies →
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.
2 replies →
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.
Why not "just" make a weaker roof steeper?