Roof Area Per Roof Drain

For a 4 hourly rainfall and 4 leader each drain can handle 4 600 sq.

Roof area per roof drain.

Calculate the total roof area by multiplying its length by width. 3 inch hr. Maximum horizontal projected roof area that can be drained in square feet. 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.

Divided by 3 460 sq. Ft therefore 29 roof drains would be required. 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.

After studying building plan and physical arrangement assume that 6 leaders are. Divided by the 4 600 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. Rainfall rate inches per hour.

Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed. 6 inch hr. Size and placement of rooftop equipment may necessitate additional roof drains. Determine leader or pipe size.

Each 4 drain size in a 6 hourly rainfall area will accommodate drainage of 3 070 sq. Flat roof drainage capacity of a single drain pipe or leader. Below to obtain roof area that can be handled by each leader. Roof pitch is a determining factor for cost of the roof as well as the roof area and the type of materials used.

A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour. 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. 4 inch hr.

This should be considered when connecting gutters and downspouts. For instance a 7 12 roof pitch means that the roof rises 7 inches for every 12 horizontal inches. Pipe cross section drainage area. It affects walkability as well as drainage and roofs in areas of high rain or snowfall tend to have steeper pitches.

Divide total roof area by area found in step 3 to obtain the number of drains required example. 1 inch hr. Calculate total roof area. Determine rate of rainfall for this example use 4.

5 inch hr. Total roof area 500 by 200 100 000 sq. 2 inch hr. Doubling the number of downspouts halves the required capacity for each.

Roof pitch affects the actual area of the roof. 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. Rainfall intensity should always be checked with the local authorities. 5 19 6 sq in.

Number of roof leaders required is 29 100 000 sq. Equals 32 6 or 33 drains required.