Calculate Rain Gutter Size

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.

Calculate rain gutter size.

The total rainfall and how rapidly it falls will affect the runoff from the roof. Refer to the gutter packaging or specification for the recommended downspout size. Then use the information below to see what size gutter you need. There is no limit to downpipe size or eaves gutter size.

Find the width of the gutters. Multiply the drainage area by the roof pitch factor and rainfall intensity to find out the adjusted square footage. Box gutter with rain water head at end of box gutter. The code limit is 150mm for dp s and 26 800 sq mm for flat eaves gutters the program will calculate the size and number of downpipes downspouts leaders required and the eaves gutter sizes for any roof.

For example a 5 inch gutter system requires at least 2 x 3 downspouts and a 6 inch gutter system requires 3 x 4 downspouts. Gather some basic weather information to calculate the proper size for gutters and downspouts for a house. Multiply the drainage area by the roof pitch factor and rainfall intensity to find out the adjusted square footage. Please lower the maximum spacing between downspouts to see this effect.

Total roof area also affects runoff. The downspout and gutter sizing calculator is located on the tools cad and apps page of the smacna website. Gutters typically come in 5 or 6 in 13 or 15 cm sizes and can be k style or half round place a sturdy 20 ft 6 1 m ladder on 1 side of your house so that you can reach the gutters. Calculations are based on level gutter capacity as experimentally determined by the national institute of standards and technology nist.

Match your downspouts to the gutter size you chose in step 7. Then use the chart below to see what size gutter you need. Downspout sizes must not exceed the bottom width of the gutter. 15 m is a practical maximum gutter length to be served by a downspout.

The gutter and downspout size required is highly dependent on the amount of gutter and the spacing of the downspouts. 6 inch 7 960 square feet. Adding additional downspouts will require less gutter and downspout volume resulting in smaller gutters downspouts. 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. 5 inch 5 520 square feet. If a roof s various drainage areas call for different size gutters go for the biggest one k style. 5 inch 5 520 square feet.