Roof Area Per Downpipe

Divide the main roof into catchments of this size and any left over area can be entered again to find a down pipe size for this smaller area.

Roof area per downpipe. This can be calculated using the following formula. The 6 in 12 pitch factor 1 1 multiplied by 1 000 yields an effective area of 1 100 square feet. Usually the size for the largest collection area on the roof is used to size downpipes throughout. Downpipe fall fall fall fall fall roof pitch 45 figure 1 an example of a roof with a total plan area of 98 m.

Roof length x half roof width x roof height 2 roof area. Using clause e1 table 5 see figure 2 at a roof pitch. From figure 3 5 a in as nzs 3500 3 the maximum catchment per downpipe is 47m 2. The answers for downpipe size are in mm.

Choosing the right style of guttering downpipes. To calculate the minimum number of downpipes divide the roof catchment area by the allowable maximum catchment per downpipe. A house in chicago has a roof whose actual drainage area is 1 000 square feet. The first thing you need to work out is the area of the roof that will collect rainfall which is known as the effective roof area.

Min number of downpipes roof catchment area. Doubling the number of downspouts halves the required capacity for each. Multiplying that number by the local maximum rainfall intensity 6 8 inches per hour yields an adjusted square footage of 7 480 square feet. Working out the size of your roof.

Determine minimum number of downpipes. Select 100 x 50 rectangular downpipe. 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.