Roof Area Per Downspout

Up to 6 12 7 12 8 12.

Roof area per downspout. Doubling the number of downspouts halves the required capacity for each. A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour. Large gutters can hold more water. Gutters come in many sizes.

Secondary cause of gutters not working properly is improperly maintained or failing. Smacna s new downspout and gutter sizing calculator enables the user to manually enter the design area of the roof or use the design area wizard for the calculation. Max area of roof draining to one down. Roof area square feet per linear ft of gutter underneath.

The table is based on rainfall intensity 100 mm per hour 4 inches per hour. A high slope moves water more quickly and if gutters have trouble dealing with a lot of water in a short period of time an extra downspout can alleviate that issue. The more roof surface above the gutters the more rainwater will be caught and funneled down into those gutters. Gutters and downspouts are vulnerable for obstructions caused branches and leafs from surrounding trees and similar.

A large roof is going to move a lot of water which means the downspout locations may need to be adjust to compensate. Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed.