Calculating Gutter And Downspout Needs

2 4 gutter and downspout sizing and location calculations.

Calculating gutter and downspout needs. Size downspouts to fit the gutter. The downspout and gutter sizing calculator is located on the tools cad and apps page of the smacna website. 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. 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.

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. Wood rot behind gutters. A damaged section of gutter. Downspout sizes must not exceed the bottom width of the gutter.

I have seen several downspouts dented or bent due to mechanical damage. Adding a 2 by 3 rectangular downspout for instance boosts your gutter s capacity by 600 square feet of drainage area. Downspouts should be constructed with conductor heads every 40 ft 12 2 m to admit air and prevent vacuum. Lots of times you will find that downspouts are missing from the gutter system.

Doubling the number of downspouts halves the required capacity for each. Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed. Size the gutters for the rainfall but go with the largest downspout that will fit your gutters. Offset of more than 10 ft 3 0 m can affect drainage capacity.

Gutters accessories. 3 by 4 inches 1 200 square. 15 m is a practical maximum gutter length to be served by a downspout. As with gutters a downspout s capacity must match or exceed the expected runoff.

And 2 the downspouts that carry the collected water to grade level. The size of the downspout should be constant through out its length. Downspout empties onto the roof. 2 by 3 inches 600 square feet.

The issue for downspouts isn t water capacity in a torrential rain it s debris that gets washed into the downspout. To limit the effects of thermal expansion in gutters 50 ft. 1 24 of 395 results for tools home improvement. The gutter outlet capacity should suit the downspout capacity.

Quite often you will see downspouts that are short and discharge onto the roof which is. This will dictate the amount of water that the gutter needs to be able to carry during the hardest rain storms. The larger the downspout the better debris will wash through. 1 gutter channels that run horizontally along the roof edge to collect runoff.

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. 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.