Parapets are a combination of wall and roof pressures.
Roof parapet height code.
2015 ibc code commentary.
However when a roof slopes down toward an exterior wall and parapet with a slope greater than 2 12 further analysis is required to determine if a taller parapet is necessary.
1 every building constructed 3 stories or 36 feet or more in height shall have roof tie backs or other permanent devices installed at the roof level for the purpose of securing or tying back suspended scaffold hooks or clamps and safety lines.
The exact height of the parapet is not factored into the roof wind uplift calculations but if the parapet is 3 or higher the perimeter values can be used at the corners lowering the uplift requirements for that portion of the roof area.
If a reinforced concrete beam is provided at the top of the wall the minimum height above the wall anchor may be 6 inches 152 mm.
The minimum height of a parapet wall above the roof surface is 30 inches.
Buildings greater than 22 feet 6706 mm in height with roof slopes less than 2 4 units vertical in 12 units horizontal 20 percent slope shall be provided with a parapet railing fence or combination thereof not less than 42 inches 1067 mm in height.
Parapet corrective work must be performed in conjunction with the installation of tension roof anchors.