Roof Area Per Roof Drain

Divide total roof area by area found in step 3 to obtain the number of drains required example.

Roof area per roof drain.

Rainfall rate inches per hour. Each 4 drain size in a 6 hourly rainfall area will accommodate drainage of 3 070 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. Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed.

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. 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. Determine leader or pipe size.

Number of roof leaders required is 29 100 000 sq. 1 inch hr. 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. After studying building plan and physical arrangement assume that 6 leaders are.

5 19 6 sq in. The table is based on rainfall intensity 100 mm per hour 4 inches per hour. Calculate total roof area. It affects walkability as well as drainage and roofs in areas of high rain or snowfall tend to have steeper pitches.

3 inch hr. 6 inch hr. For a 4 hourly rainfall and 4 leader each drain can handle 4 600 sq. Divided by the 4 600 sq.

Equals 32 6 or 33 drains required. 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. For instance a 7 12 roof pitch means that the roof rises 7 inches for every 12 horizontal inches.

Rainfall intensity should always be checked with the local authorities. Outside of the u s a degree angle is typically used. This should be considered when connecting gutters and downspouts. Maximum horizontal projected roof area that can be drained in square feet.

Calculate the total roof area by multiplying its length by width. A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour. Divided by 3 460 sq. Pipe cross section drainage area.

Area roof will require 100 000 3070 32 5 or 33 roof drains for ideal drainage. Therefore the 100 000 sq. Total roof area 500 by 200 100 000 sq. 4 inch hr.

Determine rate of rainfall for this example use 4. Gutters and downspouts are vulnerable for obstructions caused branches and leafs from surrounding trees and similar. Size and placement of rooftop equipment may necessitate additional roof drains. Doubling the number of downspouts halves the required capacity for each.

Ft therefore 29 roof drains would be required. 2 inch hr.