Calculate Rain Gutter Size

Adjusting for pitch and rainfall.

Calculate rain gutter size.

The saf perimeter systems gutter downspout capacity table click to enlarge relates downspout size to gutter sizes. Downspout sizes must not exceed the bottom width of the gutter. How to calculate gutter and downspout capacity step 1. How do you calculate gutter size.

Place a sturdy 20 ft 6 1 m ladder on 1 side of your house so that you can reach. Calculations are based on level gutter capacity as experimentally determined by the national institute of standards and technology nist. Water capacity values of a gutter downspout system is calculated using the height head of water a gutter can hold the outlet orifice size of the downspout and the quantity of downspouts used. 6 inch 7 960 square feet.

5 inch standard k style gutter shop 5 gutterbrush. Now architects engineers designers and contractors can easily and accurately size downspouts and gutters according to the specifications in smacna s architectural sheet metal manual 7th edition 2012. 5m x 4m x 4 2 40 square metres. Find the width of the gutters.

Measuring existing gutters 1. In response smacna s technical resources department has created a free downspout and gutter sizing calculator. Measure the length of each gutter run. See photos below most residential gutters will measure approximately 5 inches across the top with the actual opening being approximately 4 5 inches.

To limit the effects of thermal expansion in gutters 50 ft. 15 m is a practical maximum gutter length to be served by a downspout. 5 inch 5 520 square feet. 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 downspout and gutter sizing calculator is located on the tools cad and apps page of the smacna website. Multiply the drainage area by the roof pitch factor and rainfall intensity to find out the adjusted. The steeper a roof s pitch the more windblown rain it can collect. Then use the chart below to see what size gutter you need.

Measure the roof to get the watershed area the area from which water will run off. Box gutter with rain water head at end of box gutter. Rainfall intensity is measured in a 5 minute interval translated. Multiply length peak to.

Run the tape measure from 1 corner of the gutter as far as you can go toward. If a roof s various drainage areas call for different size gutters go for the biggest one k style. Multiply the drainage area by the roof pitch factor and rainfall intensity to find out the adjusted square footage. Find the rainfall intensity for your locale.