Gutter Downspout Requirements

A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour.

Gutter downspout requirements.

From table 1 3 it is found that a4 in 102 mm downspout is required. Divide 1600 sq ft 149 sq m by 160 sq ft sq in 2 3 sq m 100 sq mm to determine that each downspout should have a minimum area of 10 sq in 6470 sq mm. The number of downspouts will depend on the cross section dimension of the downspout material. Come visit our selection of quality products.

From chart 1 2 it is determined that a 9 5 in 241 mm half round gutter should be used. Poorly designed or installed gutters and downspouts can cause rainwater to pool around the base of the home or back up into the gutters. As with gutters a downspout s capacity must match or exceed the expected runoff. A general rule of thumb is one downspout per 20 feet of guttering but more may be necessary depending on the local weather the size of the drainage area and the design of the gutter system.

Use the chart below to figure out how many extra downspouts you need. Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed. Size downspouts to fit the gutter. The above recommendations assume that you have properly sized downspouts every 40 feet.

Welcome to gutter supply your online reference for gutters gutter machines gutter guards and accessories. Doubling the number of downspouts halves the required capacity for each.