How To Size Number Of Downspouts Needed For Roof

The size of the downspout should be constant through out its length.

How to size number of downspouts needed for roof.

To limit the effects of thermal expansion in gutters 50 ft. Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed. Rectangular downspouts move slightly less water at 600 square feet for 2 by 3 inch or 1 200 square feet for a 3 by 4 inch downspout. 5 inch 5 520 square feet.

Downspout sizes must not exceed the bottom width of the gutter. Downspouts should be constructed with conductor. 15 m is a practical maximum gutter length to be served by a downspout. Size downspouts to fit the gutter.

Multiply the number of downspouts by square footage of each. If a roof s various drainage areas call for different size gutters go for the biggest one k style. A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour. Downspouts of less than 7 00 sq in 4515 sq mm cross section should not be used except for small areas such as porches and canopies.

Downspout sizing in sizing downspouts the following considerations apply. 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. 6 inch 7 960 square feet. The capacity of a sloped rectangular gutter may be approximated by using a gutter cross section area not less than that of a semicircular gutter and a depth to width ratio of at least 0 75.

Then use the information below to see what size gutter you need. Doubling the number of downspouts halves the required capacity for each.