Calculate How Many Downspouts Gutters Need

Calculations are based on level gutter capacity as experimentally determined by the national institute of standards and technology nist.

Calculate how many downspouts gutters need.

Rainfall intensity is measured in a 5 minute interval translated. If we have to sum it up in a single rule gutters need a downspout around every 30 to 40 feet. 15 m is a practical maximum gutter length to be served by a downspout. 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. 5 gutters typically use 2 3 downspouts. How many downspout installations should your gutters have. There are many more important factors that can change this broad rule.

For most homes this means installing spouts at either end of a gutter section. Hello bb10 and welcome to the community. For hipped roofs with eaves gutters a simplified formula can be used to calculate catchment area but the slope of the roof must be known. To limit the effects of thermal expansion in gutters 50 ft.

The catchment area of a roof and any vertical walls is greatly influenced by the direction of wind driven rain therefore the combined catchment area must be used for sizing purposes. How to calculate gutter and downspout capacity step 1. Adding a 2 by 3 rectangular downspout for instance boosts your gutter s capacity by 600 square feet of drainage area. Enter larger gutter widths in the yellow boxes to find out how wide your gutters need to be given the length that you want to go between downspouts.

Adding a 2 by 3 rectangular downspout for instance boosts your gutter s capacity by 600 square feet of drainage area. As with gutters a downspout s capacity must match or exceed the expected runoff. 6 gutters typically use 3 4 downspouts to accommodate higher volume of water. 3 by 4 inches 1 200 square feet.

Refer to as nzs 3500 3. Minimum top opening width max. Once you add up the square footage of your roof you can then determine the number of downspouts. Find the rainfall intensity for your locale.

The code limit is 150mm for dp s and 26 800 sq mm for flat eaves gutters the program will calculate the size and number of downpipes downspouts leaders required and the eaves gutter sizes for any roof. Multiply length peak to. Downspout sizes must not exceed the bottom width of the gutter. 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. It is used in 95 of all installations and works for all sloped roofing materials shingles metal slate wood etc. Measure the roof to get the watershed area the area from which water will run off. The number of downspouts can be determined by the surface square feet of your roof.

There is no limit to downpipe size or eaves gutter size. Rectangular 2 by 3 inches 600 square feet 3 by 4 inches 1 200 square feet.