Calculate Rainwater Gutter Size

The gutter slope also called the pitch is the amount the gutter tilts down to let rainwater flow out of it.

Calculate rainwater gutter size.

Size downspouts to fit the gutter. Subtracting 3 4 for under the roof edge and 1 8 outside edge allowance this is the width that is available for the rainwater to enter the gutter total width of a flat piece of building material maximum total gutter drop before any downspout this assumes 4 7 per hour maximum rain intensity. If gutters don t slope water gathers in them. Calculations are based on level gutter capacity as experimentally determined by the national institute of standards and technology nist.

To limit the effects of thermal expansion in gutters 50 ft. Downspout sizes must not exceed the bottom width of the gutter. Come visit our selection of quality products. Roof often leads to oversizing of gutters downspouts and drains.

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. Cost calculator rain gutter installation calculator. Doubling the number of downspouts halves the required capacity for each. 15 m is a practical maximum gutter length to be served by a downspout.

Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed. 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. Boasting considerable experience spanning over 25 years gutter masters company has operated on different buildings scenarios and designs with success at each turn. 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.

If gutters slope too severely they don t hold water and water could splash over the sides in heavy rain. Proper gutter and downspout sizing rainfall intensity downspout capacity. A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour. Welcome to gutter supply your online reference for gutters gutter machines gutter guards and accessories.

From table 1 3 select the downspout. Simplified suitable for flattish roofs with little or no vertical faces or steep roofs draining to one side of box gutter only or any roof if you are in a hurry and make the necessary allowances for all catchments. The amount of collected water increases until it spills over the sides of the gutter.