Calculate the number of outlets per run.
How many downpipes do i need for my roof.
Frequency and positioning of outlets downpipes.
Rolls of felt are 36 wide x 144 long for 15 and 72 long for 30.
This is because larger roofs require bigger volumes of water to be diverted away from them during periods of rainfall.
The average roll of 15 pound roofing felt covers about 400 ft 2 or 4 squares while the average roll of 30 pound roofing felt covers about 200 ft 2 or 2 squares.
If a roof s various drainage areas call for different size gutters go for the biggest one k style.
A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour.
Build your roof empowers you to select each layer and component that goes into your total protection roofing system so that you get.
To calculate the average catchment per downpipe divide the roof catchment area by the number of downpipes.
5 inch 5 520 square feet.
Also the various styles of guttering that are available have different flow rates.
Always check the measurements of your building and work out exactly how much downpipe will be serving each gutter.
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The program will calculate the size and number of downpipes downspouts leaders required and the eaves gutter sizes for any roof.
Average catchment per downpipe roof catchment area.
Downpipes should not serve more than 12 metres of gutter length for each downpipe.
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.
Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed.
Multiply the drainage area by the roof pitch factor and rainfall intensity to find out the adjusted square footage.
Determine the average catchment area per downpipe.
How many rolls of felt will you need roofing felt is sold by the roll.
The code limit is 150mm for dp s and 26 800 sq mm for flat eaves gutters.
Size downspouts to fit the gutter.
Then use the information below to see what size gutter you need.
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Per downpipe 223 8 47 4 76m 2 five downpipes are required round up to the next whole number step 6.
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.
6 inch 7 960 square feet.
November 29 2019 the number of downpipes you need will depend on the size of your roof and your chosen style of guttering.
