To do that simply multiply drainage area calculated earlier by roof pitch factor and rainfall intensity.
How many square feet of roof per downspout.
For most homes this means installing spouts at either end of a gutter section.
Up to 6 12 7 12 8 12.
4 inches 1 255 square feet.
Use the chart below to figure out how many extra downspouts you 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.
3 by 4 inches 1 200 square feet.
For the vast majority of rains gutter and downspouts.
Adding a 2 by 3 rectangular downspout for instance boosts your gutter s capacity by 600 square feet of drainage area.
Measuring the square feet of the roof along with knowledge of local rainstorms is invaluable when making.
Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed.
This nominal square footage amount is then multiplied by a factor associated with the roof s pitch.
Many factors can effect the proper size of gutter.
Roof area square feet per linear ft of gutter underneath.
Gutter and downspout water capacity.
Your roof is without a doubt one of the most important elements of your home.
Roof pitches in degrees.
If we have to sum it up in a single rule gutters need a downspout around every 30 to 40 feet.
After you have calculated the square footage use following calculations.
3 inches 706 square feet.
As an example if your overhang is 12 inches you ll add 2 feet to the overall length and 2 feet to the overall width of the house.
For a 5 inch k style gutter the square footage should be up to 5 500 sq ft and for a 6 inch k style gutter the square footage should be upto 7 900 sq ft.
2 by 3 inches 600 square feet.