[Cob] roof support calculation / formula

[Clint Popetz]

On Fri, Oct 24, 2003 at 08:45:22AM -0700, Jilly wrote:
> I read allot about being careful to make sure my roof or loft area
> is properly supported, but I don't find anything on what the formula
> is to figure this out.  

Check out the "Real Goods Independent Builder" book.  It has rafter
span tables and such, which is what you need.  If you are doing a
living roof, DON'T assume 30 lbs/ft2.  That's for a typical snow-load
roof of convential materials.  Wet earth ways a lot more...depending
on the depth of earth, maybe 100 lb/ft2.

> Also, some of my cob books talk about roof pitch, like " 5 in 12 "
> What does that mean? 

That means for every 12 inches of horizontal run, the roof goes up 5
inches.  So that's about 23 degrees.

				-Clint