Roof Area Per Downpipe

A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour.

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 catchment area allowable maximum catchment per downpipe 223 8 47 4 76m five downpipes are required round up to the next whole number step 6. Choosing the right style of guttering downpipes. Frequency and positioning of outlets downpipes.

Determine the average catchment area per downpipe to calculate the average catchment per downpipe divide the roof catchmentarea by the number of downpipes. Average catchment per downpipe roof catchment area no. Calculate the number of outlets per run. 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 110mm 11 1 534 12 4 598 160mm 12 5 601 14 0 673 downpipe at end half round 76mm 0 5 24 0 6 29.

Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed. Roof length x half roof width x roof height 2 roof area. The program will calculate the size and number of downpipes downspouts leaders required and the eaves gutter sizes for any roof. Dividing the total flow from the roof by the number of downpipes will give the flow per 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. You can choose a downpipe size and calculate the number required and the corresponding eaves gutter size. To calculate the average catchment per downpipe divide the roof catchment area by the number of downpipes. 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.

It is the roof area the pitch of the roof and the number of drops downpipes coming down from outlets in the guttering around the building determine the flow we will need to know these to calculate the flow capacity for you. Doubling the number of downspouts halves the required capacity for each. Average catchment per downpipe roof catchment area there are many possibilities for downpipe positions. Dividing the total effective roof catchment area by the catchment area for the gutter selected will give the number of downpipes required.

Therefore this roof should be equipped with 6 inch k style gutters. There is no limit to downpipe size or eaves gutter size. This is not normally a whole number so it is rounded up to the nearest whole number. This can be calculated using the following formula.

The code limit is 150mm for dp s and 26 800 sq mm for flat eaves gutters. Working out the size of your roof. Of downpipes 223 8 5 44 76m. Average catchment per downpipe roof catchment area.