Gutter Downspout Requirements

Quite often you will see downspouts that are short and discharge onto the roof which is.

Gutter downspout requirements.

Adding a 2 by 3 rectangular downspout for instance boosts your gutter s capacity by 600 square feet of drainage area. Hold another elbow against the house and cut a piece of downspout to fit between the two elbows. Screw a downspout elbow to the outlet tube protruding down from the gutter. Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed.

Use the chart below to figure out how many extra downspouts you need. A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour. The number of downspouts will depend on the cross section dimension of the downspout material. Area for drainage design and they often use a square foot.

Downspout empties onto the roof. A high slope moves water more quickly and if gutters have trouble dealing with a lot of water in a short. For example if you have 30 feet of guttering the calculation is 1 4 x 3 0 75 i e. Welcome to gutter supply your online reference for gutters gutter machines gutter guards and accessories.

Wood rot behind gutters. This means the downspout end of the gutter should be set 3 4 of an inch lower than the other end. I have seen several downspouts dented or bent due to mechanical damage. Plumbing codes typically use the vertically projected roof.

Gutters and downspouts need to be sized to accommodate anticipated water loads. Come visit our selection of quality products. Size downspouts to fit the gutter. Use needlenosed pliers to slightly crimp the elbow to fit into the downspout as shown.

Allow 1 square inch of downspout cross section for every 100 square feet of roof area. From table 1 3 it is found that a4 in 102 mm downspout is required. From chart 1 2 it is determined that a 9 5 in 241 mm half round gutter should be used. As with gutters a downspout s capacity must match or exceed the expected runoff.

Doubling the number of downspouts halves the required capacity for each. Are sized in relation to rainfall on this basis. Allowance per square inch of downspout for 1 in hr 25. As a general rule gutter slope is set at 1 4 inch per 10 feet of guttering.

A damaged section of gutter. The more roof surface above the gutters the more rainwater will be caught and funneled down into those. 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. Mm hr rainfall that varies with diameter for example 3.

Lots of times you will find that downspouts are missing from the gutter system.