For the purposes of this appendix the following metric conversions are applicable.
Roof drainage calculations flat roof.
The tools guide the user step by step allowing fast and simple roof drainage design whilst ensuring full compliance with bs en12056 3 rainwater drainage design standard.
Calculate drains needed.
Size horizontal storm drainage piping.
Roof area is 200 x 500 100 000 sq.
How to calculate the quantity of drains required.
Upon completion a full set of rainwater drainage design calculations are provided confirming the suitability of products.
1 calculate the roof area to be drained.
Appendix b in the ipc provides rates of rainfall for various u s.
Gather some basic weather information to calculate the proper size for gutters and downspouts for a house.
Total roof area also affects runoff.
Select number of roof drains and calculate the roof area sloped to each drain.
Size vertical storm drainage piping.
The roof drainage outlets and rainwater downpipes are calculated based on the design principles for gravity drainage systems established in ss525 2006 code of practice for drainage of roofs.
The calculations below are meant for drainage from flat roofs where water are expected to spread over the entire flat roof during rain.
An inch of rain is not much but it if falls in half an hour it could flood a gutter.
2 estimate the roof drain outlet size you will likely use.
The total rainfall and how rapidly it falls will affect the runoff from the roof.
The full flow capacity of a drain is not realized until the water reaches approximately 2 5 above the inlet in a four inch drain and 3 5 in a six inch drain.
Roof drain system and size the scuppers denoting the required head of water above the scupper for the structural engineer.
I have found that microbursts five minute storm 10 year return period are sometimes more controlling in the sizing of the roof drainage system than a 100 year storm.
Take the roof s total square footage and divide by the total square footage handled by one drain.
1 in 25 4 mm 1 ft 305 mm 1 ft2 0 0929 m2 100 0 figure a101 1 example roof plan 4 a 101 2 solution.
The sizing of roof drains must be large enough to quickly carry away all.
The above sizing data is offered as a guide only.
The result is the number of drains needed.
Factors which affect proper roof drainage are deck slope drain size and placement of drains.
This table is based on zurn s roof drain vertical requirement for horizontal roof areas at various rainfall rates table.
Cities based on inches per hour that may fall during a storm of one hour duration and a 100 year return period.