Gutters And Downspouts Gutter Sizing Table

Table 1 2 rainfall data and drainage.

Gutters and downspouts gutter sizing table.

As with gutters a downspout s capacity must match or exceed the expected runoff. Use the chart below to figure out how many extra downspouts you need. 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. 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. As with gutters a downspout s capacity must match or exceed the expected runoff. 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 from a roof during in climate weather. Doubling the number of downspouts halves the required capacity for each.

3 by 4 inches 1 200 square feet. Offset of more than 10 ft 3 0 m can affect drainage capacity. 2 by 3 inches 600 square feet. Downspout sizing in sizing downspouts the following considerations apply.

To limit the effects of thermal expansion in gutters 50 ft. 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 downspout and gutter sizing calculator is located on the tools cad and apps page of the smacna website.

Downspout sizes must not exceed the bottom width of the gutter. 15 m is a practical maximum gutter length to be served by a downspout. Capacity from using table 1 1 and 1 2 should be com pared with local code requirements. In response smacna s technical resources department has created a free downspout and gutter sizing calculator.

Use the chart below to figure out how many extra downspouts you need. The downspout size must suit the bottom width of the gutter. The size of the downspout should be constant through. The size of semicircular gutters shall be based on the maximum projected roof area in accordance with table 1106 6.

Adding a 2 by 3 rectangular downspout for instance boosts your gutter s capacity by 600 square feet of drainage area. Rectangular 2 by 3 inches 600 square feet 3 by 4 inches 1 200 square feet. 1 inch 25 4 mm 1 square foot 0 0929 m 2. The saf perimeter systems gutter downspout capacity table click to enlarge relates downspout size to gutter sizes.

Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed. 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 a depth to width ratio of at least 0 75. The resultant calculation q cia will be the flow rate for the roof design. Table 1106 6 size of semicircular roof gutters for si.

Adding a 2 by 3 rectangular downspout for instance boosts your gutter s capacity by 600 square feet of drainage area.