Calculate Rain Gutter Size

The saf perimeter systems gutter downspout capacity table click to enlarge relates downspout size to gutter sizes.

Calculate rain gutter size.

Multiply the drainage area by the roof pitch factor and rainfall intensity to find out the adjusted. 15 m is a practical maximum gutter length to be served by a downspout. In response smacna s technical resources department has created a free downspout and gutter sizing calculator. Find the width of the gutters.

Find the rainfall intensity for your locale. 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. Downspout sizes must not exceed the bottom width of the gutter. To limit the effects of thermal expansion in gutters 50 ft.

The steeper a roof s pitch the more windblown rain it can collect. How to calculate gutter and downspout capacity step 1. 6 inch 7 960 square feet. Rainfall intensity is measured in a 5 minute interval translated.

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. Calculations are based on level gutter capacity as experimentally determined by the national institute of standards and technology nist. The downspout and gutter sizing calculator is located on the tools cad and apps page of the smacna website. Measure the length of each gutter run.

Run the tape measure from 1 corner of the gutter as far as you can go toward. How do you calculate gutter size. 5 inch standard k style gutter shop 5 gutterbrush. Measuring existing gutters 1.

Multiply length peak to. 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. Measure your gutter across the top from the back where the gutter meets the home to the outer edge. Adjusting for pitch and rainfall.

Measure the height of. 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. 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. Place a sturdy 20 ft 6 1 m ladder on 1 side of your house so that you can reach. 5m x 4m x 4 2 40 square metres. Box gutter with rain water head at end of box gutter.