Secondary Roof Drainage Design

Size vertical storm drainage piping.

Secondary roof drainage design.

When either method is used they must be sized by table 1101 12. Determine 100 year 1 hour rainfall rate used for location of building. 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. Because of that no certain distance exists.

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. This type of pattern is particularly useful on buildings that are easily divided into rectangular areas. Secondary emergency roof drain systems shall be sized in accordance with section 1106 based on the rainfall rate for which the primary system is sized. Secondary drainage secondary or emergency roof drainage is required wherever the buildup of water is detrimental to the roof 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. Roof drainage is one of the fundamental considerations of building design. The width of the opening must be equal to the circumference of the drain required. A standpipe or dam built within the secondary drain dictates the anticipated water depth.

Scuppers shall not have an opening dimension of less than 4 inches. An essential of good design. The secondary drain is typically placed about 1 2 above the depth of water above the primary at its design flow. 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.

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. Secondary drains during a roof replacement proj ect. 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.

Size horizontal storm drainage piping. 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. A scupper can be a piped penetration in the parapet wall as in figure c. The most dependable type of roof drainage design is the inverted pyramid pattern.

Overflow scuppers can also act as secondary drains at the perimeter of the roof. An open sided roof area used for secondary roof drainage can be just a simple opening in the parapet wall surrounding the roof. A secondary roof drain achieves its function by controlling the water build up. Scuppers are typically easier to install.

Scuppers shall have an opening dimension of not less than 4 inches 102 mm.