Gutter And Downspout Design Calculations

15 m is a practical maximum gutter length to be served by a downspout.

Gutter and downspout design calculations.

Downspout sizes must not exceed the bottom width of the gutter. Doubling the number of downspouts halves the required capacity for each. Table 1 1 design areas for pitched roofs pitch in ft. The gutter and downspout size requirement depends upon the number of sections and length of the gutter sections as well as the number of downspouts.

A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour. This spread sheet will help you calculate the gutter width and maximum distance between downspouts based on your maximum rainfall roof area and style of gutter. This wizard makes it easy to calculate the roof design area by providing various shape calculations and the calculation for vertical walls area per international plumbing code ipc. With 1 gpm 0 063 l s flow rate.

Experience has taught that use of the true area of a pitched roof often leads to oversizing of gutters downspouts and drains. Adding additional sections of gutter reduces the length of each section and will reduce the gutter size. The first is to make it wide and deep enough to collect all of the rainwater during the hardest rainfall. Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed.

To determine the design area for a pitched roof table 1 1 is used. Size downspouts to fit the gutter. Downspouts and gutters are sized in relation to rainfall on this basis. To limit the effects of thermal expansion in gutters 50 ft.

Calculations are based on level gutter capacity as experimentally determined by the national institute of standards and technology nist.