4 Effective Options to Drain Your Commercial Flat Roof in 2022

Many ask the question; how do you drain your flat roof?

Scupper Drain

4 Options to Drain Your Flat Roof

  • Gutters
  • Scuppers
  • Interior Drains
  • Edge Drains

The roof of your commercial business building is one of the more underrated aspects of your business as a whole, but what it represents is so much more. Sure, it can be viewed by some as just being the roof of a building, but that building represents you as a business. And the roof is what separates you and your clients and customers from the elements.

One of the most common issues with flat commercial roofs is water accumulation. Water building up anywhere on a home’s or commercial building’s roof can damage the roof. This is because water does not drain effectively, pools up, and then causes damage to both the roof and underlying structure.

This can be especially devastating when there is damage to the façade of the roof. This means that water gets into areas it is not meant to be in (think leaks) and then permeates throughout the rest of the roof. This can lead to additional water damage and potential structural damage that can be dangerous for the building and its inhabitants.

Thankfully, there are a few ways to ensure that the water drains from your flat commercial roof, keeping it free and safe from potential water damage.


One of the most commonly used solutions, gutters, are also very cost-effective solutions for drainage for flat roofs. As the water rolls off the roof’s edge, gutters catch that rainwater and then divert it down into a downspout, which dispenses the water a safe distance away from the foundation of the building.

Ultimately, this prevents rainwater from rolling off of the roof in an uncontrolled manner and running down the side of the building. That kind of uncontrolled dripping can damage things like windows, siding, and even the foundation of the building itself.

There are, however, disadvantages to using gutters as the primary drainage system on a flat roof. The first is that gutters need to have consistent cleaning to do their job effectively. When debris – like leaves – builds up in the gutter, that blocks the flow of water. When the debris is not cleaned out, the water builds up and then overflows, running down the side of the building.

Gutters are also very susceptible to damage from things like ice, severe weather, and a build-up of heavy debris. These are factors to consider when looking for drainage solutions for your flat commercial roof.


This is perhaps one of the most effective solutions for drainage for a commercial flat roof. Using this system, large square openings are made along the edge of the roof that will shoot the water safely away from the side of the building.

There can also be downspouts installed directly below the openings that are used to catch the water and drain it away from the building in a controller manner similar to the gutters.

Flat roof scuppers also have several benefits. In addition to being cost-effective, they are much easier to maintain, meaning you won’t have to clean them as you would gutters. Those wide, large scuppers will rarely get clogged by debris, and a well-designed scupper can even enhance the overall aesthetic of the building, making it look a little bit nicer than traditional gutters would.

Like anything else, however, they do have downsides. If you install the aforementioned downspouts, they risk getting clogged, and they will require regular checks for any debris build-up. They can also be quite ineffective for heavier snowmelt and rain.

Also, scuppers tend to be less effective on a flat roof with no pitch to guide the water to the edges of the building; the scuppers have to be somewhat cleverly designed to have the best overall effectiveness.

Interior Drains

These are very similar to how the drain in your sink or shower might work. These drains would be placed in the roof areas where the water is most likely to build up. The interior drains would then lead the water through a system of pipes installed below the roof and travel through the pipes until they are dispensed into a gutter or a downspout located on the side of the building.

Some very notable benefits come with using an interior drainage system. The first is that the walls and foundation of the building are protected from water damage. The second is that the pipe system is protected from damage by the roof and walls, reducing the chances of freezing or cracking. Lastly, this type of system is highly customizable, so you can get the exact type of system that you want.

There are downsides, however. It should go without saying that this is the most expensive option due to the nature of the installation and customization. Additionally, any damage that does occur has to be repaired by a professional roofing technician.

Edge Drains

This one works just as it sounds: they sit at the roof’s edge and collect the water there. It operates very similarly to a public shower. These are very similar to scupper drains in that the goal here is to prevent the water from running down the side of the building and causing any additional damage.

Edge drains are a simplistic way to divert that water from running down the side of the building, pointing the water to a predetermined destination so that it can drain safely away from the building without causing any damage.

Final Thoughts on Flat Roof Drains

Whatever the solution, drains are necessary for the life of your roof. That water build-up can lead to substantial issues over time if left unchecked, so be certain to get your drainage system in place and ensure that it is working correctly.