How Do Commercial Roof Drains Work?

Roofing Tips

commercial roof drains

When it comes to commercial and residential roofing, some elements remain the same such as the type of materials used, but aesthetically the two can be very different. Most commercial roofs are flat roofs, but in a heavy rain environment like South Florida, it can be a little confusing as to how your commercial roof drains water. With residential roofing, we know it’s generally sloped and the water slides down and into the gutter and hopefully it’s out onto the ground below, but people often wonder if the same applies to flat roofs. Is the risk of pooling water not too high? How does the water drain? Why choose a flat roof for a commercial property when this could be an issue?

For many commercial property owners, a flat roof not only works aesthetically but it is practical as well. A flat roof is more resistant to environmental factors such as freak storms or hurricanes than a sloped residential roof. One of the main challenges however is ensuring that all water is properly drained from the roof to avoid a buildup of moisture which can lead to leaks and mold and mildew growth. There are three drainage solutions for flat roof systems and each has its own pros and cons.

Interior Commercial Roof Drains

It in a nutshell, these are similar to the drains you’ll find in your bathroom and kitchen sink. They’re placed in locations on the roof that will collect the majority of the water which is then fed through a system of pipes until it reaches a gutter and will then drain out into the street.


  • The building foundation is protected from water damage.
  • The pipes are installed under the roof, protecting them from weather damage.
  • Interior drains are easily customizable according to your tastes and budget.


  • These are not a cost-effective option if you’re on a budget.
  • You will need a professional roofing contractor should anything happen to your pipes.
  • It can become easily clogged if you do not have filters on the drains to prevent debris from entering the pipe system.


These are square or round protruding openings made along the edge of the roof that drains the water away from the building. Some commercial properties will have a downspout installed directly beneath it in order to effectively manage the water disposal.


  • They are affordable.
  • It is easier to maintain than gutters or interior drains.
  • The bigger the scupper, the less likely it will be clogged by debris.
  • The design can have its own aesthetic appeal.


  • If you’re installing a downspout beneath the scupper, be aware that this can become clogged and it will need to be regularly maintained.
  • Ineffective against heavy rain.
  • The design matters, if the design is incorrect the scupper will not work.


Normal gutters, the things we all hate to clean. These are common for both commercial and residential properties and is one of the more cost-effective solutions for flat roof drainage. Water is caught as it rolls off of the edge of the roof and is then diverted to the proper downspout and out the drainage system.


  • It is affordable.
  • It is more cost effective to repair.


  • It needs regular maintenance (cleaning) all year round.
  • Can be damaged by severe weather conditions.

Remember, the drainage system you decide to implement on your commercial or residential property matters. If you have any doubts, questions or concerns you can contact the friendly, knowledgeable and reliable team at ABC Roofing Corp for all your commercial roof draining options.

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