How To Size Number Of Downspouts Needed For Roof

To limit the effects of thermal expansion in gutters 50 ft.

How to size number of downspouts needed for roof.

15 m is a practical maximum gutter length to be served by a downspout. Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed. Downspout sizes must not exceed the bottom width of the gutter. 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.

Doubling the number of downspouts halves the required capacity for each. The size of the downspout should be constant through out its length. Also the gutter width in relation to height may also be adjusted. Then use the information below to see what size gutter you need.

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. Downspouts should be constructed with conductor. Adding additional sections of gutter reduces the length of each section and will reduce the gutter size. Multiply the number of downspouts by square footage of each.

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. Size downspouts to fit the gutter. A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour.

If a roof s various drainage areas call for different size gutters go for the biggest one k style. Multiply the drainage area by the roof pitch factor and rainfall intensity to find out the adjusted square footage.