Roof Water Gutter Calculator

Roof drainage layout and calculations.

Roof water gutter calculator.

15 m is a practical maximum gutter length to be served by a downspout. To limit the effects of thermal expansion in gutters 50 ft. 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. This means the downspout end of the gutter should be set 3 4 of an inch lower than the other end.

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. These figures are based on a rainfall intensity of 75mm hr roof pitch not exceeding 50º gutters running full. Calculations are based on level gutter capacity as experimentally determined by the national institute of standards and technology nist. Divide the inch per hour watershed of the roof by the 5 minute rainfall intensity.

Calculate effective maximum roof area b c 2 x length of roof area in m installation. That will show how much water a gutter will have to drain. That is how much rain a roof can drain during the most intense rainfall. Measure the length of the gutter for downspout locations.

2 count the number of downspouts drain pipes on your house building and enter the number in downspouts field. Box gutter with rain water head at end of box gutter. Downspout sizes must not exceed the bottom width of the gutter. For example if you have 30 feet of guttering the calculation is 1 4 x 3 0 75 i e.

Ask gutter suppliers what size gutters will be needed to handle that amount. 3 select gutter type. There is no limit to downpipe size or eaves gutter size. As a general rule gutter slope is set at 1 4 inch per 10 feet of guttering.

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 use the calculator 1 measure the length of your gutters along the eaves of your roof and plug in the number in the length field. The downspout and gutter sizing calculator is located on the tools cad and apps page of the smacna website.

Roof drainage calculators our online tools have been designed with simplicity in mind removing the need for any prior specialist industry knowledge. 5m x 4m x 4 2 40 square metres. Refer to bsen 12056 part 3.