Calculating Gutter And Downspout Needs

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Calculating gutter and downspout needs.

This means the downspout end of the gutter should be set 3 4 of an inch lower than the other end. Multiply length peak to. As a general rule gutter slope is set at 1 4 inch per 10 feet of guttering. Use the chart below to figure out how many extra downspouts you need.

Remember two gutter lengths can share the same downspout so if you calculate the max gutter to be 40 feet you could put a downspout halfway in an 80 foot length. Divide 1600 sq ft 149 sq m by 160 sq ft sq in 2 3 sq m 100 sq mm to determine that each downspout should have a minimum area of 10 sq in 6470 sq mm. The gutter and downspout size required is highly dependent on the amount of gutter and the spacing of the downspouts. Ratio of depth to width of gutter calculate drainage reset.

Adding a 2 by 3 rectangular downspout for instance boosts your gutter s capacity by 600 square feet of drainage area. Max gutter per downspout ft storm requirement. For example if you have 30 feet of guttering the calculation is 1 4 x 3 0 75 i e. As with gutters a downspout s capacity must match or exceed the expected runoff.

Rainfall intensity is measured in a 5 minute interval translated. This calculator serves as an information source only. This calculator uses the equations that are laid out in the smacna handbook. Adding additional downspouts will require less gutter and downspout volume resulting in smaller gutters downspouts.

Downspout sizes must not exceed the bottom width of the gutter. Minimum top opening width max length to. To figure out what size gutters you need first you ll need to calculate the square footage of the gutter s drainage area. From table 1 3 it is found that a4 in 102 mm downspout is required.

To limit the effects of thermal expansion in gutters 50 ft. How to calculate gutter and downspout capacity step 1. 15 m is a practical maximum gutter length to be served by a downspout. Please lower the maximum spacing between downspouts to see this effect.

Measure the roof to get the watershed area the area from which water will run off. From chart 1 2 it is determined that a 9 5 in 241 mm half round gutter should be used. Metal era recommends that you verify all data obtained. The downspout and gutter sizing calculator is located on the tools cad and apps page of the smacna website.

Enter larger gutter widths in the yellow boxes to find out how wide your gutters need to be given the length that you want to go between downspouts. 2 by 3 inches 600 square feet. For a simple gable end roof you would only need to make two calculations one for each slope.