Gutter Downspout Requirements

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Gutter downspout requirements.

The number of downspouts will depend on the cross section dimension of the downspout material. From table 1 3 it is found that a4 in 102 mm downspout is required. Welcome to gutter supply your online reference for gutters gutter machines gutter guards and accessories. 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.

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

Place downspouts at least 20 feet apart but no more than 50 feet apart. From chart 1 2 it is determined that a 9 5 in 241 mm half round gutter should be used. Allow 1 square inch of downspout cross section for every 100 square feet of roof area. Poorly designed or installed gutters and downspouts can cause rainwater to pool around the base of the home or back up into the gutters.

Doubling the number of downspouts halves the required capacity for each. Use the chart below to figure out how many extra downspouts you need.