Gutter And Downspout Design Calculations

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Gutter and downspout design calculations. 2 by 3 inches 600 square feet. I certify that the roof gutter and downspout type size gage roof gutter slope and mounting. This wizard makes it easy to calculate the roof design area by providing various shape calculations and the calculation for vertical walls area per international plumbing code ipc. As with gutters a downspout s capacity must match or exceed the expected runoff.

Adding a 2 by 3 rectangular downspout for instance boosts your gutter s capacity by 600 square feet of drainage area. Once an architect has. The following is a list of the minimum required design. Calculations are based on level gutter capacity as experimentally determined by the national institute of standards and technology nist.

Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed. Remember to save this spreadsheet to your own computer. In section iv of the design guide is a sample design which includes design calculations and plan sketch. Design of roof drainage systems roof drainage the roof is one of the most essential parts of a building as it protects occupants contents and interior of the structure from the elements.

Section ii design data record on appropriate engineering paper. Doubling the number of downspouts halves the required capacity for each. A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour. 2 4 gutter and downspout sizing and location calculations both metric and english units.

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. First we will find the maximum amount of rain that will be captured in gallons per minute. Adding additional downspouts will require less gutter and downspout volume resulting in smaller gutters downspouts.

The gutter and downspout size required is highly dependent on the amount of gutter and the spacing of the downspouts. 3 by 4 inches 1 200 square. Leaking gutters and downspouts can cause serious damage to a building s interior as well as exterior and repairs can be expensive. The design of gutter and downspout assemblies is an area of building design which demands special attention.

The gutter outlet capacity should suit the downspout capacity. Size downspouts to fit the gutter. Smacna s new downspout and gutter sizing calculator enables the user to manually enter the design area of the roof or use the design area wizard for the calculation. We will use the larger of the two or 310 sq ft for our first calculation.

Use the chart below to figure out how many extra downspouts you need. Downspout sizes must not exceed the bottom width of the gutter.