Secondary Roof Drainage Design

A scupper can be a piped penetration in the parapet wall as in figure c.

Secondary roof drainage design.

Scuppers shall be sized to prevent the depth of ponding water from exceeding that for which the roof was designed as determined by section 1101 7. 3 398 380 540 380 5 3 06 in order for the 6 drain to handle the necessary flow there will be a depth of 3 06 of water above the primary drain at its peak design flow. Secondary drains during a roof replacement proj ect. From the very dawn of building construction it has been necessary to incorporate some method of gathering and discharging rainwater from the roof of a structure.

Secondary emergency overflow roof drains look similar to primary drains but a standpipe or dam blocks water from entering the drain until it reaches a certain depth. When scuppers are used for secondary emergency overflow roof drainage the quantity size location and inlet elevation of the scuppers shall be sized to prevent the depth of ponding water from exceeding that for which the roof was designed as determined by section 1611 1. Scuppers shall not have an opening dimension of less than 4 inches. Roof drainage is one of the fundamental considerations of building design.

The secondary drain is typically placed about 1 2 above the depth of water above the primary at its design flow. A standpipe or dam built within the secondary drain dictates the anticipated water depth. Secondary drainage secondary or emergency roof drainage is required wherever the buildup of water is detrimental to the roof structure. Overflow scuppers can also act as secondary drains at the perimeter of the roof.

The most dependable type of roof drainage design is the inverted pyramid pattern. An essential of good design. The width of the opening must be equal to the circumference of the drain required. An open sided roof area used for secondary roof drainage can be just a simple opening in the parapet wall surrounding the roof.

Size vertical storm drainage piping. Determine 100 year 1 hour rainfall rate used for location of building. A secondary roof drain achieves its function by controlling the water build up. For example if the roof drain is 4 in the opening of the scupper or the open sided roof opening must be 12 56 in.

Because of that no certain distance exists. Select number of roof drains and calculate the roof area sloped to each drain. Size horizontal storm drainage piping. Scuppers shall have an opening dimension of not less than 4 inches 102 mm.

This type of pattern is particularly useful on buildings that are easily divided into rectangular areas. In either case the discharge shall be located so that it is readily visible by building occupants. The premise of the pattern is that a drain is positioned in the center of the rectangular area and there is a four way positive slope into the drain. Secondary drainage shall be provided through the use of sidewall scuppers or internal roof drains.

Ipc provides four steps to size the roof drains on a building.