Divided by the 4 600 sq.
Roof area per roof drain.
4 inch hr.
Outside of the u s a degree angle is typically used.
Rainfall rate inches per hour.
5 19 6 sq in.
For a 4 hourly rainfall and 4 leader each drain can handle 4 600 sq.
For instance a 7 12 roof pitch means that the roof rises 7 inches for every 12 horizontal inches.
Area roof will require 100 000 3070 32 5 or 33 roof drains for ideal drainage.
Calculate total roof area.
3 inch hr.
6 inch hr.
Divided by 3 460 sq.
Rainfall intensity should always be checked with the local authorities.
Roof pitch affects the actual area of the roof.
It is important to remember that no roof area should ever have less than two roof drains.
The table is based on rainfall intensity 100 mm per hour 4 inches per hour.
Ft therefore 29 roof drains would be required.
Determine rate of rainfall for this example use 4.
A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour.
It affects walkability as well as drainage and roofs in areas of high rain or snowfall tend to have steeper pitches.
There are 5 easy steps to figure out how many drains your commercial roofing project will need.
Doubling the number of downspouts halves the required capacity for each.
Gutters and downspouts are vulnerable for obstructions caused branches and leafs from surrounding trees and similar.
According to the chart for 1 8 slope per 12 of pipe for 5 000 square feet of roof area with a 6 per hour of rainfall the required pipe size is 8.
Determine leader or pipe size.
Maximum horizontal projected roof area that can be drained in square feet.
Each 4 drain size in a 6 hourly rainfall area will accommodate drainage of 3 070 sq.
This should be considered when connecting gutters and downspouts.
Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed.
Size and placement of rooftop equipment may necessitate additional roof drains.
Flat roof drainage capacity of a single drain pipe or leader.
5 inch hr.
Divide total roof area by area found in step 3 to obtain the number of drains required example.
1 inch hr.
After studying building plan and physical arrangement assume that 6 leaders are.
To size the vertical roof drain for the same parameters 5 000 square feet of room area and 6 per hour of rain consult table 1106 2 figure 3.
Total roof area 500 by 200 100 000 sq.
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.
Therefore the 100 000 sq.
2 inch hr.
Equals 32 6 or 33 drains required.
Number of roof leaders required is 29 100 000 sq.
Pipe cross section drainage area.
