How Many Downpipes For Roof Area

The number of downpipes you need will depend on the size of your roof and your chosen style of guttering.

How many downpipes for roof area.

This is because larger roofs require bigger volumes of water to be diverted away from them during periods of rainfall. Downpipe fall fall fall fall fall roof pitch 45 figure 1 an example of a roof with a total plan area of 98 m. A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour. To calculate the minimum number of downpipes divide the roof catchment area by the allowable maximum catchment per downpipe.

From figure 3 5 a in as nzs 3500 3 the maximum catchment per downpipe is 47m 2. Determine minimum number of downpipes. The 6 in 12 pitch factor 1 1 multiplied by 1 000 yields an effective area of 1 100 square feet. There are many possibilities for downpipe positions.

A house in chicago has a roof whose actual drainage area is 1 000 square feet. Sizing downpipes downpipes are sized for the areas that discharge into them. How many downpipes do you need. Size downspouts to fit the gutter.

Min number of downpipes roof catchment area. Multiplying that number by the local maximum rainfall intensity 6 8 inches per hour yields an adjusted square footage of 7 480 square feet. Doubling the number of downspouts halves the required capacity for each. In some cases roof area m gutter flow litres sec roof area m downpipe at centre half round 76mm 0 7 34 0 8 38 112mm 1 8 86 2 6 125 squareflo 3 2 154 3 8 182 125 68mm downpipe 3 8 182 4 6 221 82mm downpipe 4 0 191 4 9 235 regency 4 2 202 4 7 226 highflo 5 4 258 6 0 289 stormflo.

Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed.