Secondary Roof Drainage Design

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.

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. Secondary drainage shall be provided through the use of sidewall scuppers or internal roof drains. The secondary drain is typically placed about 1 2 above the depth of water above the primary at its design flow. Select number of roof drains and calculate the roof area sloped to each drain.

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 roof drain systems shall be sized in accordance with section 1106 based on the rainfall rate for which the primary system is sized. Scuppers shall not have an opening dimension of less than 4 inches. Determine 100 year 1 hour rainfall rate used for location of building.

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. 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. Size vertical storm drainage piping.

Secondary drains during a roof replacement proj ect. An open sided roof area used for secondary roof drainage can be just a simple opening in the parapet wall surrounding the roof. Scuppers are typically easier to install. Ipc provides four steps to size the roof drains on a building.

The most dependable type of roof drainage design is the inverted pyramid pattern. Roof drainage is one of the fundamental considerations of building design. Size horizontal storm drainage piping. In either case the discharge shall be located so that it is readily visible by building occupants.

A scupper can be a piped penetration in the parapet wall as in figure c. This type of pattern is particularly useful on buildings that are easily divided into rectangular areas. 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 have an opening dimension of not less than 4 inches 102 mm.

When either method is used they must be sized by table 1101 12. 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. Because of that no certain distance exists. An essential of good design.

Overflow scuppers can also act as secondary drains at the perimeter of the roof.