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.
Roof area per roof drain.
Determine leader or pipe size.
Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed.
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.
Therefore the 100 000 sq.
A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour.
Gutters and downspouts are vulnerable for obstructions caused branches and leafs from surrounding trees and similar.
3 inch hr.
4 inch hr.
Determine rate of rainfall for this example use 4.
Roof pitch is a determining factor for cost of the roof as well as the roof area and the type of materials used.
Divided by the 4 600 sq.
For instance a 7 12 roof pitch means that the roof rises 7 inches for every 12 horizontal inches.
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.
Doubling the number of downspouts halves the required capacity for each.
1 inch hr.
5 inch hr.
The table is based on rainfall intensity 100 mm per hour 4 inches per hour.
Pipe cross section drainage area.
Maximum horizontal projected roof area that can be drained in square feet.
After studying building plan and physical arrangement assume that 6 leaders are.
This should be considered when connecting gutters and downspouts.
Calculate the total roof area by multiplying its length by width.
Rainfall intensity should always be checked with the local authorities.
It affects walkability as well as drainage and roofs in areas of high rain or snowfall tend to have steeper pitches.
Each 4 drain size in a 6 hourly rainfall area will accommodate drainage of 3 070 sq.
Divide total roof area by area found in step 3 to obtain the number of drains required example.
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.
5 19 6 sq in.
Flat roof drainage capacity of a single drain pipe or leader.
There are 5 easy steps to figure out how many drains your commercial roofing project will need.
Rainfall rate inches per hour.
Ft therefore 29 roof drains would be required.
Below to obtain roof area that can be handled by each leader.
Number of roof leaders required is 29 100 000 sq.
Calculate total roof area.
Divided by 3 460 sq.
Equals 32 6 or 33 drains required.
Area roof will require 100 000 3070 32 5 or 33 roof drains for ideal drainage.
Outside of the u s a degree angle is typically used.
For a 4 hourly rainfall and 4 leader each drain can handle 4 600 sq.
Total roof area 500 by 200 100 000 sq.
