Once you add up the square footage of your roof you can then determine the number of downspouts.
How many downspouts do i need on my garage gutters.
Many think they don t need gutters on their garage as long as they have them on the rest of their house.
For most homes this means installing spouts at either end of a gutter section.
First you must consider how many downspouts you will need.
3200 square feet of roof is calculated as 3200 600 5 33 rounding up you would need 6 2x3 downspouts.
Use the chart below to figure out how many extra downspouts you need.
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.
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.
The number of downspouts can be determined by the surface square feet of your roof.
Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed.
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.
Installing gutters on a house make sense but do you really need gutters on a detached garage.
Adding a 2 by 3 rectangular downspout for instance boosts your gutter s capacity by 600 square feet of drainage area.
Size downspouts to fit the gutter.
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 square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour.
Why installing gutters on a garage is important.
The typical recommendation is one downspout for every 20 to 30 feet of gutters.
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.
Rectangular 2 by 3 inches 600 square feet 3 by 4 inches 1 200 square feet.
Adding a 2 by 3 rectangular downspout for instance boosts your gutter s capacity by 600 square feet of drainage area.
As with gutters a downspout s capacity must match or exceed the expected runoff.
3 by 4 inches 1 200 square feet.
Doubling the number of downspouts halves the required capacity for each.
Use the chart below to figure out how many extra downspouts you need.
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.
