Roof Area Per Roof Drain

Converting this to gallons per minute per square foot gpm ft 2.

Roof area per roof drain.

Roof area is 300 x 500 ft. 300 x 500 150 000 sq. Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed. Size downspouts to fit the gutter.

Walls that drain onto a lower storey roof can increase the effective roof area by around 50. Determine rate of rainfall for this example use 4. Total roof area 500 by 200 100 000 sq. When sizing roof drains the limiting factor for the amount of water each drain will carry away is the size of leader therefore increasing leader size decreases the number of drains required.

1 inch of rainfall in an hour will cover 1 sq ft. Calculate total roof area. Required roof drainage flow rate in gallons per minute 0 0104 x rainfall rate x roof area where rainfall rate is expressed in inches per hour and roof area is given in square feet. Determine leader or pipe size.

A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour. 4 roof drain 3 determine your building s location on the above map to determine the approximate rainfall as measured in inches per hour. Roof drainage systems need to be designed to cope with the rainfall intensities for the specific building location. Rainfall intensities vary throughout new zealand and are often very high.

The above result is the number of roof drains required for the building. Drainage design specific to location. Divide the total roof area by the area that one leader will handle. There are 5 easy steps to figure out how many drains your commercial roofing project will need.

The number of roof drains shown should be verified with local code requirements. The speed at which the rain collects at the drain. Doubling the number of downspouts halves the required capacity for each. 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.

Step by step sizing of zurn drains step 1. If the result is a fraction less use the next higher number. Calculate total roof area. The roof drain calculator below is based on the maximum amount of rainfall in inches per hour of the hypothetical worst storm in the past 100 years and which has a two percent chance of occurring in any given year.

Roof area is 200 x 500 100 000 sq.