Roof Area Per Downpipe

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

Roof area per downpipe.

Using clause e1 table 5 see figure 2 at a roof pitch. A house in chicago has a roof whose actual drainage area is 1 000 square feet. Select 100 x 50 rectangular downpipe. Sizing downpipes downpipes are sized for the areas that discharge into them.

This can be calculated using the following formula. From figure 3 5 a in as nzs 3500 3 the maximum catchment per downpipe is 47m 2. Determine minimum number of downpipes. 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. Working out the size of your roof. Choosing the right style of guttering downpipes. Multiplying that number by the local maximum rainfall intensity 6 8 inches per hour yields an adjusted square footage of 7 480 square feet.

To calculate the minimum number of downpipes divide the roof catchment area by the allowable maximum catchment per downpipe. Downpipe fall fall fall fall fall roof pitch 45 figure 1 an example of a roof with a total plan area of 98 m. Doubling the number of downspouts halves the required capacity for each. The answers for downpipe size are in mm.

The 6 in 12 pitch factor 1 1 multiplied by 1 000 yields an effective area of 1 100 square feet. A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour. 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 length x half roof width x roof height 2 roof area.