Maximize Flat Roof Drainage Efficiency: Expert Tips

Flat roofs can make any building instantly unique, whether it’s a home in your neighborhood or a cityscape full of towering office buildings. They’re durable, resistant to severe weather, and can easily turn any roof into an outdoor living space or swoon-worthy rooftop garden. But when it rains or snows, where does all that fallen precipitation go? What wizardry do flat roofs use to ensure that water is properly diverted from the building and its foundation?

The answer is simple: since flat roofs don’t have the advantage of slope and gravity to remove water, they need to use a drainage system of sorts to help get the job done. In fact, there are three main drainage solutions that work wonderfully with flat roofs, and each has its pros and cons. Let’s explore them below!

Interior Drains

This type of drainage system is often found on the roofs of large buildings, but they may also be used for residential homes. Think of them like the drain in your sink or shower. They use an interior system of pipes, which can be found below the roof, to carry water away from the home’s foundation. The drains are typically placed in the center of the roof.


  • The pipe system is protected by the roof and walls of the building. This minimizes the pipes’ risk of bursting, cracking, or freezing.
  • This drainage system effectively protects your walls and foundation from water damage.
  • The system is customizable and can easily boost your curb appeal with custom fittings.


  • Interior drains are the costliest of all flat roof drainage systems.
  • Even though interior drains are less susceptible to damage, you will need to have a professional roofing technician make any repairs to damage that may occur.
  • You’ll need to remain extra vigilant since debris can easily clog the system. We advise installing strainers to help prevent blockage and checking the system routinely – otherwise, you may face standing water on your roof.


Gutters are the most commonly used drainage system when it comes to flat roofs. Just like the gutters installed on sloped roofs, these marvels catch rainwater and divert it into a downspout, which carries it away from the foundation.


  • Inexpensive and universal, gutters are the easiest drainage system to find and install.
  • This system helps prevent water from pouring off the roof in heavier rains, protecting walls, doorways, and window openings.
  • Gutters work wonders in keeping water away from the building, preventing insidious water damage.


  • Gutters can pull away from fascia boards over time.
  • Gutters are susceptible to damage from ice, heavy debris, and severe weather.


Scuppers are essentially large square openings in the outer walls or curbs along a building’s roofline. These openings allow water to flow from the side of the building. It isn’t unusual for scuppers to be installed with downspouts directly below the openings to catch water and divert it away from the building.


  • When appropriate, scuppers are the best choice for efficiently draining water from a flat roof.
  • It’s a cost-effective system that’s easy to maintain and rarely experiences clogging (if they are large and wide enough).
  • Scuppers can enhance the architectural appeal of any building.


  • If you have downspouts installed below the scuppers, they will need to be checked regularly since they can clog.
  • Scuppers may not be as effective in downpours and snowmelt.

Which is Right for Your Flat Roof?

Any of these systems will effectively divert water from your flat roof, provided it is installed correctly and properly maintained. It’s important to strongly consider each drainage system’s pros and cons before you make your decision, including cost, durability, and maintenance requirements. When in doubt, consider your building type and location to help you determine the best drainage system for your flat roof.

If you’re still unsure which system to choose, the friendly experts at Ferguson Roofing have your back. Rely on us to help you choose and install the right system for your roof! Call us today at (314) 521-6917 in Missouri or (618) 212-1912 in Illinois to learn more.