How To Size Number Of Downspouts Needed For Roof

Size downspouts to fit the gutter.

How to size number of downspouts needed for roof.

Downspouts should be constructed with conductor. 15 m is a practical maximum gutter length to be served by a downspout. The size of the downspout should be constant through out its length. 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.

Multiply the drainage area by the roof pitch factor and rainfall intensity to find out the adjusted square footage. 5 inch 5 520 square feet. Downspout sizes must not exceed the bottom width of the gutter. Also the gutter width in relation to height may also be adjusted.

Then use the information below to see what size gutter you need. Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed. 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.

Adding additional sections of gutter reduces the length of each section and will reduce the gutter size. Doubling the number of downspouts halves the required capacity for each. 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. 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. To limit the effects of thermal expansion in gutters 50 ft.