How Many Downspouts Are Needed For Gutters

3 by 4 inches 1 200 square feet.

How many downspouts are needed for gutters.

As with gutters a downspout s capacity must match or exceed the expected runoff. Rectangular 2 by 3 inches 600 square feet 3 by 4 inches 1 200 square feet. 2 by 3 inches 600 square feet. Adding a 2 by 3 rectangular downspout for instance boosts your gutter s capacity by 600 square feet of drainage area.

First you must consider how many downspouts you will need. 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. Doubling the number of downspouts halves the required capacity for each.

Poorly designed or installed gutters and downspouts can cause rainwater to pool around the base of the home or back up into the gutters. Adding a 2 by 3 rectangular downspout for instance boosts your gutter s capacity by 600 square feet of drainage area. Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed. As with gutters a downspout s capacity must match or exceed the expected runoff.

The gutter troughs and downspouts must be installed with this pitch in mind so that water flows down instead of remaining stagnant in the gutter trough. If we have to sum it up in a single rule gutters need a downspout around every 30 to 40 feet. There are many more important factors that can change this broad rule. Use the chart below to figure out how many extra downspouts you need.

The typical recommendation is one downspout for every 20 to 30 feet of gutters. 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. A general rule of thumb is one downspout per 20 feet of guttering but more may be necessary depending on the local weather the size of the drainage area and the design of the gutter system.