Ways To Make Your Commercial Flat Roof Drain Effectively

15 June 2022
 Categories: , Blog


Thinking of installing a flat roof on your commercial building? Flat roofing systems are the most preferred option for commercial buildings because of multiple reasons, including fast installation, increased safety, and cost-effectiveness.

On the downside, drainage can be a big challenge with flat roofs, especially in areas that receive abundant annual rainfall.

The good news is that it's possible to ensure good drainage on flat roofs. However, this requires a proper roof design. Here are some things that roof installers do to prevent drainage issues with commercial flat roofs.

Positive Drainage

An integral part of a good roof drainage system is to ensure the roof has positive drainage. Positive roof drainage means the roof has a minimum slope to allow proper drainage.

For flat roofs, positive drainage means avoiding ponding water on the roof. It does not mean that rainwater will clear from the roof immediately after a storm. 

Gutter Installation

Like other commercial roofing systems, flat roofs use gutters and downspouts to facilitate efficient drainage.

Running along the lower edges of a flat roof, gutters collect roof runoff – the rain that falls on the roof's surface. The water from the gutters is directed away from the foundation of the building via downpipes – the rainwater pipes that run down the side of the building. 

Gutters and downpipes require regular cleaning to maintain proper roof drainage. Regular cleaning of gutter systems helps keep them clear of dirt and debris that may cause them to clog up and stop working well.

Internal Drainage System

Often located in the center of roofing systems, internal drains are an effective way to move water away from a flat roof. These drains are connected to plumbing that runs within the building to lead water away.

As they are covered by the roof, internal drains are an aesthetically pleasing option for your commercial flat roof. On the downside, they can be difficult to access when it's time for maintenance and repairs. 


As one of the simplest, cheapest, and oldest methods of roof drainage, scuppers describe openings in the sidewall of a building. These openings are usually adjusted to align with the roof slope and are used along with gutters and downspouts to prevent water damage to the building.

Scuppers can become clogged because they are open, so regular maintenance is essential. 

Need a quote for your commercial flat roof installation? Reach out to a commercial roofing contractor today!