How To Figureout Number Roof Drain For A Flat Roof

Roof pitch affects the actual area of the roof.

How to figureout number roof drain for a flat roof. A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour. Rainfall rate inches per hour. 1 calculate the roof area to be drained. This information can be obtained from the pipe or drain manufacturer.

Select number of roof drains and calculate the roof area sloped to each drain. 2 estimate the roof drain outlet size you will likely use. Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed. Roof pitch is a determining factor for cost of the roof as well as the roof area and the type of materials used.

Doubling the number of downspouts halves the required capacity for each. Calculate the total roof area by multiplying its length by width. 5 inch hr. Size horizontal storm drainage piping.

Conversely the larger the drain outlet diameter the fewer you will need. It is important to remember that no roof area should ever have less than two roof drains. When placing roof drains it is good design practice to locate the drains no more than 50 feet from the roof perimeter nor more than 100feet apart. 4 inch hr.

3 inch hr. Determine leader or pipe size. Next the roof area is divided by the area for each leader to determine the number of drains required. 4 roof drain 3.

2 inch hr. 1 inch hr. Pipe cross section drainage area. The more drains you will need.

5 19 6 sq in. There are 5 easy steps to figure out how many drains your commercial roofing project will need. Size downspouts to fit the gutter. 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.

How to calculate the quantity of drains required. Ipc provides four steps to size the roof drains on a building. It affects walkability as well as drainage and roofs in areas of high rain or snowfall tend to have steeper pitches. The next step is to determine each roof area that will be served by a separate leader drain pipe scupper or downspout.

The calculations below are meant for drainage from flat roofs where water are expected to spread over the entire flat roof during rain. 6 inch hr. Determine 100 year 1 hour rainfall rate used for location of building. Size and placement of rooftop equipment may necessitate additional roof drains.

Roof area is 200 x 500 100 000 sq. Using tools from the international plumbing code ipc it s not that hard.