How To Size Number Of Downspouts Needed For Roof

Doubling the number of downspouts halves the required capacity for each.

How to size number of downspouts needed for roof.

Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed. 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. The size of the downspout should be constant through out its length.

5 inch 5 520 square feet. Multiply the drainage area by the roof pitch factor and rainfall intensity to find out the adjusted square footage. 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. If a roof s various drainage areas call for different size gutters go for the biggest one k style.

Then use the information below to see what size gutter you need. To limit the effects of thermal expansion in gutters 50 ft. Size downspouts to fit the gutter. 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.

15 m is a practical maximum gutter length to be served by a downspout. Downspout sizes must not exceed the bottom width of the gutter. 6 inch 7 960 square feet. Downspouts should be constructed with conductor.

A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour. Also the gutter width in relation to height may also be adjusted.