Roof Drainage Calculations Flat Roof

Take the roof s total square footage and divide by the total square footage handled by one drain.

Roof drainage calculations flat roof.

2 estimate the roof drain outlet size you will likely use. Factors which affect proper roof drainage are deck slope drain size and placement of drains. I downloaded installed and tried out harmer drainage s free roof drainage calculator for a flat roof choosing a roof drain product line which has implications of drain pipe diameter and thus capacity geographic area the tool can plug in rainfall rates for the u k and i used an assumed a roof area of 10x10m 100 m2. The sizing of roof drains must be large enough to quickly carry away all.

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. Cities based on inches per hour that may fall during a storm of one hour duration and a 100 year return period. Roof area is 200 x 500 100 000 sq. Gather some basic weather information to calculate the proper size for gutters and downspouts for a house.

The total rainfall and how rapidly it falls will affect the runoff from the roof. Select number of roof drains and calculate the roof area sloped to each drain. This table is based on zurn s roof drain vertical requirement for horizontal roof areas at various rainfall rates table. Size vertical storm drainage piping.

How to calculate the quantity of drains required. That calculation is rather easy as it is based on a severe storm and the rainwater flow rate from the roof surface to the roof drain. Roof drain system and size the scuppers denoting the required head of water above the scupper for the structural engineer. 1 calculate the roof area to be drained.

Appendix b in the ipc provides rates of rainfall for various u s. The above sizing data is offered as a guide only. Total roof area also affects runoff. An inch of rain is not much but it if falls in half an hour it could flood a gutter.

Calculate drains needed. Upon completion a full set of rainwater drainage design calculations are provided confirming the suitability of products. The calculations below are meant for drainage from flat roofs where water are expected to spread over the entire flat roof during rain. The result is the number of drains needed.

For the purposes of this appendix the following metric conversions are applicable. Size horizontal storm drainage piping. 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. 4 roof drain 3 determine your building s location on the above map to determine the approximate rainfall as measured in inches.