Roof drainage systems are designed to channel rainwater that lands on the roof safely away from the building. In this blog, the roofing contractors at Vertex Roofing Contractors Inc. share a primer on how these drainage systems work on flat and low-slope roofs.
Sloped Vs. Flat Roofing Drainage
Residential roofing systems are traditionally sloped, which means gravity plays a big role in directing rainwater toward the gutters. With flat or low-slope roofs, gravity isn’t much help, so the drainage systems need to be more sophisticated. Manual pdf
Since commercial properties are often larger than residential ones, installing a single sloped roofing system is often impractical. Even at minimum slope, it would make the building extremely tall. The resulting attic space would be difficult to insulate and maintain, while roof repair would be difficult and expensive. Installing multiple slopes would require complicated drainage systems that would be very difficult to maintain. This is why most commercial properties have flat roofs.
Basics of Flat Roofing Drainage
It’s worth noting that the name “flat roof” is somewhat of a misnomer as no roof is completely flat; a slight slope is necessary for drainage. This is why the terms “low-slope” and “flat” roofing are often used interchangeably. Manual pdf Due to the design, flat roofs are more susceptible than sloped roofs to pooling water, accumulating twigs and leaves and developing leaks near penetrations such as vent pipes.
There are three types of drainage systems that can be installed on flat roofs:
- Interior Drains — Interior drains are similar to storm drains and are usually located at the lower end of the slope. They lead into downspouts that may either be embedded in the building facade or on it.
- Gutters — Certain types of gutters are compatible with flat and low-slope roofs. Gutters require regular cleaning and maintenance to perform properly.
- Scuppers — Scuppers are large openings that route rainwater away from the roofing surface. They need to be strategically located so that the runoff doesn’t collect near the building’s foundations.