[Strawbale] Death in collapsing SB house

[Sherwood Botsford]

We recently redid one wing of our house in steel instead of 
asphalt shingles.  One of the advantages is the erratic self 
cleaning feature.  Admittedly when you wake up in the middle of 
the night to a sliiiiiddde  whooootsh THUMP it can be startling.

I have a tractor shed that I made 5 years ago that is a crudely
framed roof with only a Princess Auto tarp covering it all.  BUT 
it is a 1:1 ratio roof as opposed to  the usual 1:3 or 1:4 ratio
roof.  It is unusual for more than 1" of snow to stick to it.
More often it slides when the snow gets to be about a centimeter.

Question for the people familiar with roof truss engineering and
codes:  With a metal roof, what is the cheapest slope to make the 
roof?  E.g.  1:1 slides very quickly with negligible load on the 
roof.  1:3 slides, but it takes it's time.  The slope that 
guarantees sliding may well be cheaper to build because it 
doesn't need to support such a large live load.

As an example, by tractor shed uses 2 16" 2x6 and 1 7.5 foot 2x6
as an A-frame.  This gives me a span of just under 22 feet.  The
peak joint is gusseted 2' x 2' triangles of 3/8" OSB.  The 
A-frame joints are just nailed with 5 4" ardox nails each.
Trusses are set on 32" centres.  Horizontal purlons of 1x4
run every 2 feet on the outside face.  Inside a pair of diagonal
1x4's run to give it a bit of stability.