Roof Area Per Roof Drain

5 19 6 sq in.

Roof area per roof drain.

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. Rainfall rate inches per hour. Determine rate of rainfall for this example use 4.

Doubling the number of downspouts halves the required capacity for each. Number of roof leaders required is 29 100 000 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. Maximum horizontal projected roof area that can be drained in square feet.

Calculate the total roof area by multiplying its length by width. Roof pitch affects the actual area of the roof. Gutters and downspouts are vulnerable for obstructions caused branches and leafs from surrounding trees and similar. Total roof area 500 by 200 100 000 sq.

Calculate total roof area. 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. 6 inch hr.

There are 5 easy steps to figure out how many drains your commercial roofing project will need. 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. Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed.

Below to obtain roof area that can be handled by each leader. 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. This should be considered when connecting gutters and downspouts. 5 inch hr.

1 inch hr. Size and placement of rooftop equipment may necessitate additional roof drains. 3 inch hr. It affects walkability as well as drainage and roofs in areas of high rain or snowfall tend to have steeper pitches.

Equals 32 6 or 33 drains required. 4 inch hr. Pipe cross section drainage area. Divide total roof area by area found in step 3 to obtain the number of drains required example.

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. 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. Divided by the 4 600 sq.

Determine leader or pipe size. After studying building plan and physical arrangement assume that 6 leaders are. Divided by 3 460 sq. Therefore the 100 000 sq.

Outside of the u s a degree angle is typically used. Area roof will require 100 000 3070 32 5 or 33 roof drains for ideal drainage.