Flat roofing systems offer a number of benefits, specifically giving you more space for storage or even rooftop gardens. Flat roofing is ideal for warmer climates and not areas where there is a lot of rainfall; it is perfect in the Los Angeles area. As with all roofing systems, flat roofing has its good and bad qualities, and there are often problems with the drainage that you should be aware of.

Flat Roof Drain System Pros and Cons

Types of Drains for Flat Roofing

The interesting thing about flat roofing is that it is not entirely flat. There is always a slight slope towards the drain. Gravity is what allows the drainage system to work, so the water needs to have a natural flow away from the roof. Despite this, there are common drainage problems associated with flat roofing:

  • Foundation problems
  • Infiltration of water into living spaces
  • Water damage to walls and casings

These problems may be common, but there are still numerous advantages to having flat roofing and each type of drain system has its own pros and cons.

  • Inner drains: These sit away from the edge towards the center of the roof. There is a pipe system below the drain that shuttles the water away. Often these can form pools of water on the surface if there are any clogs to the system and the heavy water can eventually find a way into the building. These drains are also more expensive and repairs can be costly. On the positive side, they are great for colder climates as the pipes do not freeze. There is also the benefit of having a clean roofline as the system is away from the edges.
  • Scuppers: These are small boxed drains that exit through the parapet wall. The slight slope of the roof allows water and debris to move along the roof and out the scupper. Like inner drains, these too can become clogged and if water pools near the roof edge, it can spill over. If they are not connected to a downspout, then water can damage your foundation as it falls, eroding the surface. These drains are not very expensive and when you get a wider variety, they are easier to maintain and prevent from clogging.
  • Gutters: These metal structures sit along the edge of the roof, collecting water as it flows down the slope. These not only help protect your foundation but they help to control the flow of water away from the roof. They are inexpensive and are the best way to protect your foundation, basement, and soils from erosion. These do however require frequent maintenance to prevent clogs and it is wise to have leaf guards for easier cleaning.


Flat roofing is a great choice for any building, just be sure you have the appropriate drainage system in place too. The top three choices have pros and cons, so discuss your options with the professionals and we’ll help you decide which drainage system is best for your needs and your flat roof.

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