Understanding Basic Commercial Roof Drainage Systems

Proper drainage is key to commercial roof longevity. However, the flatter the slope, the more prone it is to pooling water. Considering that a one-inch pond can weigh 5.2 pounds per square foot, it can put a great strain on the roof. When left unchecked for 48 hours, the roofing system can collapse due to hydrostatic pressure.

Understanding Basic Commercial Roof Drainage Systems

So what’s the best drainage system for a flat-roofed structure? If you ask experienced commercial roofers, like Alpine Roofing Construction, here are your best bets:

Interior Drains

Similar to those used in bathroom and kitchen water fixtures, they’re connected to the plumbing system. They collect rainwater from the roof and direct it to a series of pipes until it reaches gutters that safely expel them away from the building.

Since they’re not exposed to the weather, interior pipes are virtually impervious to the outdoor elements. The way they’re installed also helps protect your building’s foundations from water damage.


Placed along the edge of the low-slope roof, these protruding openings are in prime locations to drain rainwater efficiently. Generally, commercial roofers consider them one of the more affordable options. In addition, they demand the least maintenance. The bigger they are, the less susceptible they are to debris accumulation.

Downspouts can be added to facilitate water disposal, but they render upkeep a bit trickier. Plus, their efficiency decreases during heavy downpours.


Like in sloped roofs, gutters lend themselves to flat ones too. When their size and pitch are perfect, honest commercial roofers would agree that they can handle large amounts of water. The downside is that they’re constantly under threat of weather damage. Fortunately, they render repairs a breeze because they’re easily accessible.

Let Alpine Roofing Construction help you determine the most suitable drainage system for your flat-roofed building. Call us at (214) 380-4607 to discuss your roofing needs and get a free estimate. We serve Arlington, Dallas and Fort Worth, Texas, as well as the other neighboring TX communities.

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