a gable roof is double pitched with vertical ends
The most recommended type of foundation for a sloping site is a step foundation. It provides stability while adding style.
Purlins are used on double roofs. They effectively reduce the span of the rafters and limit their size to ecenomical sections.
too many variables here, mostly the size of the roof above it (steepness, weight of shingles, tile or slate? etc. You're best to overengineer it. A double thickness (3.5" X 12" or 16" wide) glulam will support a reasonably large roof above it, otherwise a simple double 2x12 would work for a 3/12 -6/12 pitch roof with light grade 30 year shingles.
About 5metres(16') but would have to be stress graded timber.
gable end??
A roof that is pitched off horizontal to allow the runoff of water, snow, or ice.
a Chalet
To shed snow.
it called the saltbox
It's a Leanto yay pogo
Valley
Sloping roofs are self-draining from rain and snow, and less likely to leak.
A roof/
A roof with only two sloping surfaces and gables at each end is called a gable roof.
Full length of the roof line is called a Dutch Dormer.
Anywhere there is a lot of snow fall. A flat roof will cave in under the weight of significant snowfall.