Parapet Roof Drainage Design

From a roof edge.

Parapet roof drainage design.

Adding a parapet wall makes a flat roof far safer than leaving the roof s edge exposed. Working with manufacturers will help develop your understanding but don t delegate your design responsibility to them. Install a drain at most 50 ft. Provide adequate flashing for parapets openings walls joints skylights etc.

With a parapet wall it is possible for a roof to retain or pond water should the primary roof drainage system fail. However these days parapets add a lot more to a flat roof than just a cosmetic detail. Roofs of this design will have one or more roof drains or scuppers installed. Parapet and valley gutters are treated differently because they have a higher risk of failure.

Watch for clogs blockage at the roof drain or scupper. This would be in situations where a retaining wall or parapet prevents direct access to the roof s edge. In these cases the. Requires a primary drainage system with.

This kind of drainage system is most common on small flat roofs where water volume and buildup isn t extreme. 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. Install a drain at most 50 ft.

The drainage requirements for flat roofs on buildings present some special problems that we describe and illustrate here. It s also sometimes used in tandem with scuppers. Looking at a building from the ground a parapet may seem to simply be a design choice that adds little more than a characteristic look to a building. Buildings that incorporate flat roofs with centralized roof drains and internal downspouts are another story.

The most dependable type of roof drainage design is the inverted pyramid pattern. Limit the number of parapet walls. Keep the distance between drains to at most 200 ft. At page top and at left our photos show a low slope roof surrounded by a parapet.

However parapets block the drainage of rainwater from freely flowing over the roof edge. This type of pattern is particularly useful on buildings that are easily divided into rectangular areas. Typically surrounded with parapet walls to screen roof top equipment and to provide. 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.

On larger and more complex schemes specialist consultants may be employed to design the rainwater drainage system. In many cases these buildings have parapet walls that surround the perimeter of the roof.