Calculate Rain Gutter Size

To limit the effects of thermal expansion in gutters 50 ft.

Calculate rain gutter size. 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. Please lower the maximum spacing between downspouts to see this effect. If a roof s various drainage areas call for different size gutters go for the biggest one k style.

6 inch 7 960 square feet. The gutter and downspout size required is highly dependent on the amount of gutter and the spacing of the downspouts. Then use the chart below to see what size gutter you need. 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.

15 m is a practical maximum gutter length to be served by a downspout. Determine the size of your downspout. 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.

There is no limit to downpipe size or eaves gutter size. Refer to the gutter packaging or specification for the recommended downspout size. Multiply the drainage area by the roof pitch factor and rainfall intensity to find out the adjusted square footage. 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.

5 inch 5 520 square feet. 5 inch 5 520 square feet. The total rainfall and how rapidly it falls will affect the runoff from the roof. Downspout sizes must not exceed the bottom width of the gutter.

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. Match your downspouts to the gutter size you chose in step 7. Then use the information below to see what size gutter you need. An inch of rain is not much but it if falls in half an hour it could flood a gutter.

The downspout and gutter sizing calculator is located on the tools cad and apps page of the smacna website. Total roof area also affects runoff. 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.