Adding a 2 by 3 rectangular downspout for instance boosts your gutter s capacity by 600 square feet of drainage area.
How many downspouts do i need on my garage gutters.
Once you add up the square footage of your roof you can then determine the number of downspouts.
2 by 3 inches 600 square feet.
A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour.
In areas with heavy rainfall your installer may also determine that for optimal flow you want downspouts on each end of a gutter run even if it s only about 20 feet.
A common mistake made by homeowners in an attempt to save money time and effort is to skip the installation of a gutter system on their garage.
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.
First you must consider how many downspouts you will need.
Adding a 2 by 3 rectangular downspout for instance boosts your gutter s capacity by 600 square feet of drainage area.
Doubling the number of downspouts halves the required capacity for each.
As with gutters a downspout s capacity must match or exceed the expected runoff.
The number of downspouts can be determined by the surface square feet of your roof.
Whether the garage is built on a concrete slab or is supported by a full foundation adding gutters to a garage s roof does the same thing they do on your home direct water safely away from the foundation.
Why installing gutters on a garage is important.
Most gutter installers add a downspout about every 20 or 30 feet of gutter although depending on the slope of your roof and the rooflines you may need more.
Installing gutters on a house make sense but do you really need gutters on a detached garage.
Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed.
If we have to sum it up in a single rule gutters need a downspout around every 30 to 40 feet.
For most homes this means installing spouts at either end of a gutter section.
Many think they don t need gutters on their garage as long as they have them on the rest of their house.
3200 square feet of roof is calculated as 3200 600 5 33 rounding up you would need 6 2x3 downspouts.
3 by 4 inches 1 200 square feet.
Size downspouts to fit the gutter.
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.
The typical recommendation is one downspout for every 20 to 30 feet of gutters.
Use the chart below to figure out how many extra downspouts you need.
