Calculate Rainwater Gutter Size

Proper gutter and downspout sizing rainfall intensity downspout capacity.

Calculate rainwater gutter size.

Downspout sizes must not exceed the bottom width of the gutter. Cost calculator rain gutter installation calculator. If gutters slope too severely they don t hold water and water could splash over the sides in heavy rain. Come visit our selection of quality products.

Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed. To determine the design area multiply the plan area by the factor in b column these areas are then divided by the proper factor given in table 1 2 thus obtaining the required area in square inches square mm for each downspout. To limit the effects of thermal expansion in gutters 50 ft. If gutters don t slope water gathers in them.

Roof often leads to oversizing of gutters downspouts and drains. The gutter slope also called the pitch is the amount the gutter tilts down to let rainwater flow out of it. Boasting considerable experience spanning over 25 years gutter masters company has operated on different buildings scenarios and designs with success at each turn. A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour.

Calculations are based on level gutter capacity as experimentally determined by the national institute of standards and technology nist. To determine the design area for a pitched roof table 1 1 is used. Doubling the number of downspouts halves the required capacity for each. The amount of collected water increases until it spills over the sides of the gutter.

From table 1 3 select the downspout. Box gutter with rain water head at end of box gutter. In many parts of the country rain gutters are an absolute must and are integral in keeping water out of basements and preventing damage to homes. Size downspouts to fit the gutter.

15 m is a practical maximum gutter length to be served by a downspout. To determine the design area multiply the plan area by the factor in b column these areas are then divided by the proper factor given in table 1 2 thus obtaining the required area in square inches. However in areas like san diego orange county and other parts of southern california we are often praying for rain and do not seem to get enough rainfall to cause builders to automatically add a.