Rain Water Gutter Size

Multiply the drainage area by the roof pitch factor and rainfall intensity to find out the adjusted square footage.

Rain water gutter size.

The gutter and downspout size requirement depends upon the number of sections and length of the gutter sections as well as the number of downspouts. Also the gutter width in relation to height may also be adjusted. Measure your gutter across the top from the back where the gutter meets the home to the outer edge. Size downspouts to fit the gutter.

6 inch 7 960 square feet. Doubling the number of downspouts halves the required capacity for each. Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed. See photos below most residential gutters will measure approximately 5 inches across the top with the actual opening being approximately 4 5 inches.

Five inch k style gutters or 6 inch half rounds the most common residential sizes are able to handle the rainfall on most houses in most parts of the country. Most downspouts are rectangular but they can also be round or square. Gutter downspout sizes are 3 to 6 inches. But houses with big steep roofs or those located in climates prone to heavy downpours may need wider gutters and extra downspouts to keep rainwater from overflowing.

If a roof s various drainage areas call for different size gutters go for the biggest one k style. Adding additional sections of gutter reduces the length of each section and will reduce the gutter size. Then use the chart below to see what size gutter you need. 5 inch 5 520 square feet.

To limit the effects of thermal expansion in gutters 50 ft 15 3 m is a practical maximum length of gutter to be served by a downspout. The larger a gutter downspout the more water it can drain quickly. However too large a gutter downspout can look unattractive. A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour.