Once the drainage system is determined the designer must ensure positive drainage by correctly positioning the roof drains.
Pto roof drain spacing.
A good rule to follow is to provide two roof drains for a total roof area less than 10 000 square feet.
The roof drain or gutter or drain piping or downspout leader size diameter other size constraints e g.
If insulation thickness exceeds 1 taper 18 from the drain bowl.
The required parameters for the drain spacing calculator with typical values for the upper midwest and a reference diagram are as follows.
Z110 green roof drain shown with 18 height for intensive green roofing applications.
2 500 4 x 3 75 2 344 sq ft.
Mechanically fasten all tapers using two fasteners per board.
If insulation layer is 1 or less taper 12 from the drain bowl.
The full flow capacity of a drain is not realized until the water reaches approximately 2 5 above the inlet in a four inch drain and 3 5 in a six inch drain.
Or 12 drains required.
Take the roof s total square footage and divide by the total square footage handled by one drain.
Z110 green roof drains are available with enclosure heights ranging from 5 to 18 or as specified.
The result is the number of drains needed.
The international code council icc is a non profit organization dedicated to developing model codes and standards used in the design build and compliance process.
Enter table 1108 1 until you find a diameter pipe that will carry 2 344 sq ft.
A minimum 4 inch vertical drain is required.
For example in the u k.
Each vertical drain must carry 2 500 sq ft of roof area at 3 75 inches per hour of rainfall.
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.
50 000 4 400 11 36.
Taper roof insulation to drain sumps using tapered edge strips.
The international codes i codes are the widely accepted comprehensive set of model codes used in the us and abroad to help ensure the engineering of safe sustainable affordable and resilient structures.
To convert to an area for a 4 inch per hour rainfall to enter table 1108 1 do this.
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.
Typical range 0 25 to 0 5 inches day.
The drainage coefficient is the design capacity of the drainage system and is typically expressed as a depth of water removed in 24 hours inches day.
An additional roof drain should be added for each 10 000 square foot area.
