Calculate Rain Gutter Size

If a roof s various drainage areas call for different size gutters go for the biggest one k style.

Calculate rain gutter size. Multiply the drainage area by the roof pitch factor and rainfall intensity to find out the adjusted. The downspout and gutter sizing calculator is located on the tools cad and apps page of the smacna website. Place a sturdy 20 ft 6 1 m ladder on 1 side of your house so that you can reach. Rainfall intensity is measured in a 5 minute interval translated.

The steeper a roof s pitch the more windblown rain it can collect. 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. Adjusting for pitch and rainfall. See photos below most residential gutters will measure approximately 5 inches across the top with the actual opening being approximately 4 5 inches.

Measure the roof to get the watershed area the area from which water will run off. Calculate the area of a roof to work out how much guttering is required so for a roof that is 5 m long with a height of 4 m and the roof width is 8 m which makes the half roof width 4m we can calculate the effective roof area like this. How to calculate gutter and downspout capacity step 1. 15 m is a practical maximum gutter length to be served by a downspout.

Measuring existing gutters 1. Multiply length peak to. Multiply the drainage area by the roof pitch factor and rainfall intensity to find out the adjusted square footage. How do you calculate gutter size.

In response smacna s technical resources department has created a free downspout and gutter sizing calculator. 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. Find the width of the gutters. Then use the chart below to see what size gutter you need.

5m x 4m x 4 2 40 square metres. Box gutter with rain water head at end of box gutter. 6 inch 7 960 square feet. Run the tape measure from 1 corner of the gutter as far as you can go toward.

Find the rainfall intensity for your locale. Downspout sizes must not exceed the bottom width of the gutter. Calculations are based on level gutter capacity as experimentally determined by the national institute of standards and technology nist. The saf perimeter systems gutter downspout capacity table click to enlarge relates downspout size to gutter sizes.

Measure the length of each gutter run. To limit the effects of thermal expansion in gutters 50 ft. 5 inch 5 520 square feet. Measure the height of.