commercial roof

Commercial roof drainage systems are vital to keep your commercial building free from water damage. Knowing how the systems work will make it easier to determine the best system for you and your maintenance needs, in order to prevent any problems.

How It Works

The type of commercial roof drain you have will be dependent on your building and the type of roof. The three types of drainage systems are gutters, internal roof drains and scuppers.

  • Gutters – Gutters are the most common drainage systems you will see on residential homes and commercial buildings with sloping roofs. The water rolls off the incline of the roof and into the gutter along the edge. It is then funneled away from the building through downspouts. A flat roof may have gutters and downspouts but just as often you will find internal roof drains or scuppers.
  • Internal Roof Drains – The internal drains are drains positioned throughout the roof, in areas that will collect water, usually by design. A drainage pipe is run from the roof drain into a storm sewer system and away from the building. The roof drain is topped with a dome strainer that helps prevent any debris from clogging the drain. The strainer will need to be maintained and cleaned out to allow the water to flow freely away from the building. With this type of drain, once installed, there is not usually a need for replacing pipes or other costly maintenance
  • Scupper – A scupper is a hole in the parapet wall of a building through which the water from a roof can drain. Usually the roof is designed with a slope toward a wall and diverted by use of crickets to a series of square holes called scuppers. The scuppers allow water to flow through the wall and into a collection box and from there into a downspout. The scupper and collection box are often areas where debris collect.


All three types of drainage systems need a maintenance schedule and should be maintained by a professional roofing company. . Keeping a roof free of debris and water will allow your roof drainage system to work properly, and a simple inspection and maintenance visit from Jewett Roofing Company in St. Louis will help to protect your property from potential costly repairs.

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