How does water run off a flat roof?

Updated February 21, 2017

A flat roof is commonly used on many buildings, especially those that house businesses. Slanted roofs are typically only seen on homes, and are considered more of a decoration. However, a flat roof creates many challenges for the owner. The main problem is in the area of rainfall. Water has to run off of the roof to keep it from leaking down through the ceiling and into the building below. But while water can easily run off a slanted roof, a flat roof impedes the process. It is important to find a way to get rid of the water before it does any damage to the building.

What Can Cause a Flat Roof to Leak?

Not all flat roofs leak. Many, in truth, are not completely flat. If the building was designed so that the roof has even a slight incline to it, the water will run off and not have time to collect and leak through the ceiling. Other roofs are made of strong materials the water cannot seep through, unless an extremely large amount of moisture collects on it. Just because a building has a flat roof doesn't necessarily mean there will be any problem.

How Does Water Run Off a Flat Roof?

For those flat roofs that do have problems with water, several steps can be taken in increase runoff. First, consider having a coating applied that can help keep leaks from occurring. Adhesives are available that can help trap the water out. The main way water can run off a flat roof is through a drain system. Having drains and gutters installed correctly will direct the water into the drains, which will in turn let the water pour harmlessly onto the ground below. Water can also be drained by having the roof built up slightly, to allow it to drain better. A combination of these alternatives allows water to run easily off of the roof.

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