Miami’s sunny skies often yield to rain, and then you hope the flat roof of your commercial property is up to the task of draining all that water. If you realize your so-called “flat roof” is actually a low-slope roof, you will better understand how a flat roof drains water. Knowing a bit about your roof can also help you avoid flat roof repair from ponding and drainage issues.

 What do Drainage Systems do?

A low-slope roof tilts slightly downhill from its center or from one side, so water rolls off to parapet scuppers and down the hopper (downspout). The scuppers are the openings in the outside walls, specifically designed to allow water, but not debris, to wash off your roof.

Internal drains are often placed in low-slope roofs when the roof span does not make a single slope practical. The roof slopes toward the center drain, where pipes in your building channel the water into the sewage system.

An efficient low-slope roof drainage system works entirely by gravity, because water always seeks the lowest level. Ensure your drains are the lowest points on your flat roof, and you can avoid water infiltration and subsequent flat roof repair.


The drains must allow a large volume of water (equal to the square footage of your roof times the number of inches of rain) to drain quickly. Any clog in the internal drain or scuppers leads to ponding, where water simply sits on your roof. The water weight compresses roof insulation, leading to more ponding.

To avoid flat roof repair, consider the value of flat roof maintenance and inspection. After a major storm, semiannually and anytime you suspect roof damage, contact PSI Roofing to arrange a complete inspection. Usually, small problems caught in time can save you the cost of extensive flat roof repair work.

Our crews will clear debris from the strainers (also called birdcages) covering the internal drains, check for signs of water infiltration, and replace the entire drain head if necessary.

Scuppers, gutters and downspouts also must be clear of debris for water to move off your Miami property’s roof. Once most of the water volume has drained, natural evaporation will leave the roof surface dry.

PSI Roofing has the experience, crews and equipment necessary to complete an inspection of your Miami roof today. Contact our offices to discuss ways we can help solve your drainage problems and preserve your roof.

Learn more about your roof:

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