Inches of rise per foot of run For example, a 45-degree roof has twelve inches of rise for each foot of run and is therefore called a "twelve pitch" roof
a term used to express the ratio of a roof's vertical rise in inches to each foot of run-the horizontal distance Even "flat" roofs need a minimum pitch of 1/4 inch in 1 foot for drainage
The angle of a roof expressed as a rise in inches per 12 inches (i e : 4 in 12 - means the roof rises vertically 4 inches for every 12 inches of horzontal distance)