Roof Area Per Roof Drain

Pipe cross section drainage area.

Roof area per roof drain. For a 4 hourly rainfall and 4 leader each drain can handle 4 600 sq. Roof pitch is a determining factor for cost of the roof as well as the roof area and the type of materials used. It affects walkability as well as drainage and roofs in areas of high rain or snowfall tend to have steeper pitches. Divided by 3 460 sq.

3 inch hr. Outside of the u s a degree angle is typically used. Divide total roof area by area found in step 3 to obtain the number of drains required example. It is important to remember that no roof area should ever have less than two roof drains.

6 inch hr. Determine leader or pipe size. 2 inch hr. Rainfall intensity should always be checked with the local authorities.

Area roof will require 100 000 3070 32 5 or 33 roof drains for ideal drainage. Size and placement of rooftop equipment may necessitate additional roof drains. Below to obtain roof area that can be handled by each leader. Therefore the 100 000 sq.

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. Each 4 drain size in a 6 hourly rainfall area will accommodate drainage of 3 070 sq. For instance a 7 12 roof pitch means that the roof rises 7 inches for every 12 horizontal inches. Total roof area 500 by 200 100 000 sq.

1 inch hr. 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. The table is based on rainfall intensity 100 mm per hour 4 inches per hour. Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed.

Gutters and downspouts are vulnerable for obstructions caused branches and leafs from surrounding trees and similar. After studying building plan and physical arrangement assume that 6 leaders are. Maximum horizontal projected roof area that can be drained in square feet. 4 inch hr.

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. Equals 32 6 or 33 drains required. Doubling the number of downspouts halves the required capacity for each. Number of roof leaders required is 29 100 000 sq.

Calculate total roof area. Ft therefore 29 roof drains would be required. 5 inch hr. 5 19 6 sq in.

Flat roof drainage capacity of a single drain pipe or leader. A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour. Roof pitch affects the actual area of the roof. Rainfall rate inches per hour.

This should be considered when connecting gutters and downspouts. Determine rate of rainfall for this example use 4.