Parapet Roof Drainage Design

Adding a parapet wall makes a flat roof far safer than leaving the roof s edge exposed.

Parapet roof drainage design.

Working with manufacturers will help develop your understanding but don t delegate your design responsibility to them. Install a drain at most 50 ft. From a roof edge. Even without parapet walls the pitch of a flat roof and the location of a drain can be such that failure of the drain would allow water to collect on the roof.

P1106 5 design and install per fbc plumbing. Select number of roof drains and calculate the roof area sloped to each drain. However these days parapets add a lot more to a flat roof than just a cosmetic detail. It s also sometimes used in tandem with scuppers.

Scuppers are used to provide an outlet through parapet walls or gravel stops on flat and built up roofs to allow drainage of excess water. Hvhz so the code does allow scuppers as primary elements. Roofs of this design will have one or more roof drains or scuppers installed. From the edge of a valley.

This would be in situations where a retaining wall or parapet prevents direct access to the roof s edge. With a parapet wall it is possible for a roof to retain or pond water should the primary roof drainage system fail. Size vertical storm drainage piping. On larger and more complex schemes specialist consultants may be employed to design the rainwater drainage system.

The drainage requirements for flat roofs on buildings present some special problems that we describe and illustrate here. They can be used in conjunction with gutters and downspouts to divert the flow to the desired location. Appendix b in the ipc provides rates of rainfall for various u s. Install a drain at most 50 ft.

Parapet and valley gutters are treated differently because they have a higher risk of failure. At page top and at left our photos show a low slope roof surrounded by a parapet. Limit the number of parapet walls. This kind of drainage system is most common on small flat roofs where water volume and buildup isn t extreme.

Cities based on inches per hour that may fall during a storm of one hour duration and a 100 year return period. If a building has roof access that residents use regularly for whatever reason adding a parapet greatly decreases the chance that someone could fall over the. Manually adjust roof planes to have a negative pitch to create a parapet wall structure with a center drain. Watch for clogs blockage at the roof drain or scupper.

Keep the distance between drains to at most 200 ft. Size horizontal storm drainage piping. Provide adequate flashing for parapets openings walls joints skylights etc. Parapet wall roof drainage scupper location shall comply with the florida fire prevention code.