Calculate How Many Downspouts Gutters Need

Keeping gutters in good condition is more important than many people realize.

Calculate how many downspouts gutters need.

A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour. Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed. One 3x4 downspout will drain 1200 sq. Rectangular 2 by 3 inches 600 square feet 3 by 4 inches 1 200.

Doubling the number of downspouts halves the required capacity for each. Adding a 2 by 3 rectangular downspout for instance boosts your gutter s capacity by 600 square feet of drainage area. Smaller gutters may need extra downspouts to make up for their low volume. On average two hundred feet of gutter and 50 feet of downspout will cost approximately 2250.

As with gutters a downspout s capacity must match or exceed the expected runoff. 3 by 4 inches 1 200 square. Of gutters and downspouts you will be spending about 1 500 1 800. Cost of aluminum gutters and downspouts.

Cost of vinyl gutters and downspouts. Particularly wet climates could require better drainage systems than relatively dry climates rainy. Not only can runoff from a roof ruin landscaping next to a building it may cause erosion that will damage the foundation. Heavy rainstorms put a lot more pressure on gutters.

Use the chart below to figure out how many extra downspouts you need. 3200 square feet of roof is calculated as 3200 600 5 33 rounding up you would need 6 2x3 downspouts or 3200 square feet of roof is calculated as 3200 1200 2 67 rounding up you would need 3 3x4 downspouts one 2x3 downspout will drain 600 sq. Typically professionally installed aluminum seamless gutters cost 10 12 per linear foot. So if you need to install 150 ln ft.

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. Size downspouts to fit the gutter. Aluminum is the most popular choice for gutter material because it s lightweight and durable.

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. Prices range from 6 12 per linear foot for both gutters and downspouts. Elbows miters end caps gutter outlets gutter wedges gutter offsets coil sheet goods gutter hangers downspout brackets gutter flashings gutter fasteners conductor leader heads aluminum soffit trim gutter decorations downspout guards accessories paint sealant solder polish tile. From time to time rain gutters wear out and must be replaced.

Gutters come in many sizes. In terms of material options most seamless gutters roughly 80 of all installs are made from aluminum. 2 by 3 inches 600 square feet.