2 by 3 inches 600 square feet.
Calculating gutter and downspout needs.
For example if you have 30 feet of guttering the calculation is 1 4 x 3 0 75 i e.
This means the downspout end of the gutter should be set 3 4 of an inch lower than the other end.
Rainfall intensity is measured in a 5 minute interval translated.
Minimum top opening width max length to.
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.
From chart 1 2 it is determined that a 9 5 in 241 mm half round gutter should be used.
Max gutter per downspout ft storm requirement.
Ratio of depth to width of gutter calculate drainage reset.
As with gutters a downspout s capacity must match or exceed the expected runoff.
Please lower the maximum spacing between downspouts to see this effect.
15 m is a practical maximum gutter length to be served by a downspout.
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.
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.
Multiply length peak to.
From table 1 3 it is found that a4 in 102 mm downspout is required.
As a general rule gutter slope is set at 1 4 inch per 10 feet of guttering.
Downspout sizes must not exceed the bottom width of the gutter.
How to calculate gutter and downspout capacity step 1.
To limit the effects of thermal expansion in gutters 50 ft.
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.
Measure the roof to get the watershed area the area from which water will run off.
Calculations are based on level gutter capacity as experimentally determined by the national institute of standards and technology nist.
This calculator serves as an information source only.
Use the chart below to figure out how many extra downspouts you need.
Adding a 2 by 3 rectangular downspout for instance boosts your gutter s capacity by 600 square feet of drainage area.
3 by 4 inches 1 200 square feet.
To figure out what size gutters you need first you ll need to calculate the square footage of the gutter s drainage area.
Find the rainfall intensity for your locale.
