How Many Downspouts For Roof

Rainfall intensity should always be checked with the local authorities.

How many downspouts for roof.

As with gutters a downspout s capacity must match or exceed the expected runoff. Buried or underground roof drainage downspout defects clogging overflowing holes corrosion leaks that cause wet basements or crawl areas proper installation of buried downspout extensions proper installation of french drains seepage pits at flat sites gutter downspout defects cause wet basements crawl areas questions answers about installing maintaining repairing buried roof. For most homes this means installing spouts at either end of a gutter section. 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.

There are many more important factors that can change this broad rule. Determine leader or pipe size. As with gutters a downspout s capacity must match or exceed the expected runoff. Use the chart below to figure out how many extra downspouts you need.

Doubling the number of downspouts halves the required capacity for each. The typical recommendation is one downspout for every 20 to 30 feet of gutters. Rectangular 2 by 3 inches 600 square feet 3 by 4 inches 1 200 square feet. Gutters and downspouts are vulnerable for obstructions caused branches and leafs from surrounding trees and similar.

How many downspout installations should your gutters have. Calculate the total roof area by multiplying its length by width. The next factor to take into account is the pitch of your roof because the pitch will cause water to flow in a certain direction. 3200 square feet of roof is calculated as 3200 600 5 33 rounding up you would need 6 2x3 downspouts or 3200 square feet of roof is calculated as 3200 1200 2 67 rounding up you would need 3 3x4 downspouts one 2x3 downspout will drain 600 sq.

First you must consider how many downspouts you will need. A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour. Smacna s new downspout and gutter sizing calculator enables the user to manually enter the design area of the roof or use the design area wizard for the calculation. One 3x4 downspout will drain 1200 sq.

Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed. Adding a 2 by 3 rectangular downspout for instance boosts your gutter s capacity by 600 square feet of drainage area. There are 5 easy steps to figure out how many drains your commercial roofing project will need. The above recommendations assume that you have properly sized downspouts every 40 feet.

Size downspouts to fit the gutter.