Calculating Gutter And Downspout Needs

I have seen several downspouts dented or bent due to mechanical damage.

Calculating gutter and downspout needs.

Lots of times you will find that downspouts are missing from the gutter system. Wood rot behind gutters. Downspout sizes must not exceed the bottom width of the gutter. Size downspouts to fit the gutter.

As you proceed keep in mind the different areas of your roof that you measured in section 2 2 calculating your roof area for rainwater harvesting. 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. 3 by 4 inches 1 200 square.

The capacity of a sloped rectangular gutter may be approximated by using a gutter cross section area not less than that of a semicircular gutter and. The size of the downspout should be constant through out its length. Gutter systems consist of two parts. 2 by 3 inches 600 square feet.

Size the gutters for the rainfall but go with the largest downspout that will fit your gutters. 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. A damaged section of gutter. Roofing gutters should slope down toward the downspout at the rate of 1 16 inch per foot or 1 4 inch per 5 to 10 feet.

Gutters accessories. To limit the effects of thermal expansion in gutters 50 ft. Use the chart below to figure out how many extra downspouts you need. The larger the downspout the better debris will wash through.

Downspout empties onto the roof. Quite often you will see downspouts that are short and discharge onto the roof which is. Gutter downspouts welcome to the gutter downspouts store where you ll find great prices on a wide range of different gutter downspouts for your home. 1 24 of 395 results for tools home improvement.

This will dictate the amount of water that the gutter needs to be able to carry during the hardest rain storms. The gutter outlet capacity should suit the downspout capacity. Downspouts should be constructed with conductor heads every 40 ft 12 2 m to admit air and prevent vacuum. 2 4 gutter and downspout sizing and location calculations.

The issue for downspouts isn t water capacity in a torrential rain it s debris that gets washed into the downspout. And 2 the downspouts that carry the collected water to grade level. Adding a 2 by 3 rectangular downspout for instance boosts your gutter s capacity by 600 square feet of drainage area. The downspout and gutter sizing calculator is located on the tools cad and apps page of the smacna website.

Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed. 15 m is a practical maximum gutter length to be served by a downspout.