Rain Water Gutter Size

See photos below most residential gutters will measure approximately 5 inches across the top with the actual opening being approximately 4 5 inches.

Rain water gutter size.

Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed. Unless special provisions are made for flexibility in downspouts rain gutters and their support systems gutters should expand away from downspouts and downspouts should not be located near gutter expansion joints. Gutter downspout sizes are 3 to 6 inches. Also the gutter width in relation to height may also be adjusted.

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. 5 inch 5 520 square feet. Then use the chart below to see what size gutter you need. 6 inch 7 960 square feet.

Measure your gutter across the top from the back where the gutter meets the home to the outer edge. A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour. However too large a gutter downspout can look unattractive. Most downspouts are rectangular but they can also be round or square.

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. Size downspouts to fit the gutter. Doubling the number of downspouts halves the required capacity for each. Use this handy guide to make sure your rain collection is up to the task during even the heaviest storm.

The larger a gutter downspout the more water it can drain quickly. Adding additional sections of gutter reduces the length of each section and will reduce the gutter size. You should have enough gutter downspouts to effectively handle the size of your entire gutter system. Multiply the drainage area by the roof pitch factor and rainfall intensity to find out the adjusted square footage.