The Best Drainage Systems for Flat Commercial Roofs

Commercial flat roofs are great for ease of maintenance, durability, and cost-effectiveness, but all of these benefits hinge on effective drainage. Without an effective means to remove moisture from rain, snowmelt, and any other source, the water can pool and accelerate deterioration and cause leaks and further damage. This can drastically reduce the roofing system’s service life. This makes choosing the right drainage system just as important as choosing the roofing system itself. There are three excellent options that roofing contractors have found to work great for flat roofing systems, so let’s take a look at all three of them so you can decide which is best for your roof.

Interior Drains

An interior drain system is composed of a series of drains placed strategically at locations in the center of the commercial roof with a system of pipes and gutters to transport the water to the exterior of the structure. This drainage system typically uses either strainers or toppers to protect the vulnerable interior pipes from leaves and other debris that could clog the pipes and gutters.

Due to the tendency of water to collect at the center of flat roofing systems, this works great for large commercial roofing systems. Also, because the system is hidden on the interior of the roof, it is an extremely aesthetically pleasing solution as well. However, though this system is efficient and attractive, it does have the downside of being relatively costly to install and maintain.


Gutters are the most common drainage solution for sloped and flat roofs alike. These are highly effective drainage systems that most people are highly familiar with. These open-topped drainage pipes run along the outer edge of the roofing system to collect water and direct it away from the building.

This system is highly cost-effective; however, it may require the roofing system to be modified to add a slight pitch to direct water toward the gutters. These can handle any amount of moisture and are easy to maintain, but they will require regular cleaning and maintenance to remove debris.


There is a good chance you have seen water gushing from the sides of commercial buildings during periods of heavy rain, particularly on older structures. These water outlets are referred to as scuppers, and they can be a highly effective method of drainage. These drainage outlets are located along the outer sides of a building and are best paired with a slight slope to direct water toward them.

This drainage system is more affordable than an interior pipe system, albeit slightly more costly than gutters. They are great at directing water away from the building and its foundation, but they do require some maintenance and cleaning to keep debris from clogging them.

Final Thoughts

Proper drainage is key to an effective flat roofing system. With proper drainage, water is directed away from the building protecting the structure from harmful pooling and leaks. This makes it critical to choose a high-quality drainage system.

Contact Us

For installation or maintenance of a flat roof drainage system, contact North Shore Roofing. Our experienced roofing technicians have decades of roofing experience and are fully licensed and insured. Call us at (978) 977-3816 and connect with us on Facebook.