Gutter Downspout Capacity

Water capacity values of a gutter downspout system is calculated using the height head of water a gutter can hold the outlet orifice size of the downspout and the quantity of downspouts used.

Gutter downspout capacity.

Downspout sizes must not exceed the bottom width of the gutter. The risk of rain gutter overflow from insufficient drainage capacity. Van mark brakes ladder max stabilizer outlet punches gutter mate nail hawg end cap crimpers soldering irons accessories downspout crimpers snips hand seamers hand notchers drill bits chuck drivers gloves folding tools gutter nail driver rivet gun 3 8 awl large grip 12 combination. As with gutters a downspout s capacity must match or exceed the expected runoff.

Use the helpful charts below and you ll be a near expert in no time. The downspout size must suit the bottom width of the gutter. Adding a 2 by 3 rectangular downspout for instance boosts your gutter s capacity by 600 square feet of drainage area. How to make sure your gutter is large enough and you have enough downspouts.

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. 3 by 4 inches 1 200 square. A scupper serving a designated roof area ï after the number and location of downspouts have been determined the areas to be drained by each downspout should be figured. 2 by 3 inches 600 square feet.

Adding a 2 by 3 rectangular downspout for instance boosts your gutter s capacity by 600 square feet of drainage area. Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed. The gutter outlet capacity should suit the downspout capacity. 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.

15 m is a practical maximum gutter length to be served by a downspout. Doubling the number of downspouts halves the required capacity for each. Use the chart below to figure out how many extra downspouts you need. As with gutters a downspout s capacity must match or exceed the expected runoff.

To limit the effects of thermal expansion in gutters 50 ft. Rectangular 2 by 3 inches 600 square feet 3 by 4 inches 1 200. Size downspouts to fit the gutter. A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour.

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 downspout and gutter sizing calculator is located on the tools cad and apps page of the smacna website. So what s the trick to designing the perfect gutter system. It is possible to use a mix of gutter sizes a mix of downspout sizes and quantities to accommodate the theoretical gallons per minute draining.