Rainwater Gutter Design Calculations

Resources aluminum series acm series column covers fastener series zinc series testing data aama pdf astm pdf gutter sizing sheet metal gages order literature northclad gutter size requirement calculator this calculator uses current data to calculate the required size of gutter as well as number and size of downspouts based on your input.

Rainwater gutter design calculations. Downspout sizes must not exceed the bottom width of the gutter. Smacna s new downspout and gutter sizing calculator enables the user to manually enter the design area of the roof or use the design area wizard for the calculation. Roof drainage layout and calculations. Working out gutter slope as a general rule gutter slope is set at 1 4 inch per 10 feet of guttering.

This wizard makes it easy to calculate the roof design area by providing various shape calculations and the calculation for vertical walls area per international plumbing code ipc. To limit the effects of thermal expansion in gutters 50 ft. Calculate effective maximum roof area b c 2 x length of roof area in m installation tips for gutter fixings onto wooden fascias use 25mm x no 10 round head rust proof screws. 15 m is a practical maximum gutter length to be served by a downspout.

Overflow provisions rain shadow roof slopes how to find rainfall intensity how to calculate the area of any catchment how to find the hydraulic grade of charged pipes how to design box gutters using the code how to use the extra features of the dp calculator box gutters allowable width slope length other plumbing codes how to exceed the. We recommend resource library read more. This means the downspout end of the gutter should be set 3 4 of an inch lower than the other end. Divide these areas by the local rain fall rate in inches per hour to determine the actual roof area to be served by the gutter diameter.

Size downspouts to fit the gutter. Calculations are based on level gutter capacity as experimentally determined by the national institute of standards and technology nist. Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed. Design area wizard.

On a rainfall intensity of 75mm hr roof pitch not exceeding 50º gutters running full. A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour. Refer to bsen 12056 part 3. Area and flow in table 1 4 are based on 1 in 25 mm of rainfall per hour.

For the most up to date rain intensity data visit noaa s website and use precipitation intensity as the data type. From chart 1 2 it is determined that a 9 5 in 241 mm half round gutter should be used. For example if you have 30 feet of guttering the calculation is 1 4 x 3 0 75 i e.