Roof Area Per Downpipe

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.

Roof area per downpipe.

To calculate the minimum number of downpipes divide the roof catchment area by the allowable maximum catchment per downpipe. Doubling the number of downspouts halves the required capacity for each. Select 100 x 50 rectangular downpipe. Multiplying that number by the local maximum rainfall intensity 6 8 inches per hour yields an adjusted square footage of 7 480 square feet.

The answers for downpipe size are in mm. Using clause e1 table 5 see figure 2 at a roof pitch. Working out the size of your roof. Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed.

Min number of downpipes roof catchment area. A house in chicago has a roof whose actual drainage area is 1 000 square feet. The 6 in 12 pitch factor 1 1 multiplied by 1 000 yields an effective area of 1 100 square feet. From figure 3 5 a in as nzs 3500 3 the maximum catchment per downpipe is 47m 2.

Sizing downpipes downpipes are sized for the areas that discharge into them. The program will calculate the most suitable circular and rectangular downpipe sizes. Choosing the right style of guttering downpipes. A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour.

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. 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. Usually the size for the largest collection area on the roof is used to size downpipes throughout.