Question 768390: The pitch of a roof is the ratio of the rise to the half-span. If a roof has a rise of 8 feet and a span of 20 feet, what is the pitch? Answer by fcabanski(1391) (Show Source): You can put this solution on YOUR website! A fraction is a ratio. In this case it's rise/half-span. Half-span means the amount of horizontal distance the roof covers from the highest point to the edge.
If the span is 20 feet, the half span is 10 feet. The ratio is 6/20 which can be reduced to 3/10.
Roofers/carpenters and other building contractors often call this 6 in 20 which means 6 feet of rise for every 20 feet of horizontal span.