How Does a Drainage System Function on a Commercial Flat Roof?

Drainage System Function on a Commercial Flat Roof

The main job of a commercial roof is to protect the building from the outside weather and Mother Nature’s wrath, such as UV Rays and heavy rains. But what protects the roof from damage, particularly water damage? It is common knowledge that residential buildings’ slanted roofs do not have to face issues like stagnant water, which leads to water damage. These slanted roofs benefit from gravity / gravity-driven gutter systems to get rid of water.

But what about the flat commercial roofs in Redding? Commercial roofs need a different kind of drainage system to remove stagnant water. In this blog, we are going to learn more about the type of drainage systems used on commercial flat roofs and how they function. But first, let’s talk a little about the importance of having a flat roof drainage system.

Side Effects Of Water Ponding On Your Flat Commercial Roof

Without proper drainage on your roof, there can be many negative issues, the major one being water ponding/ standing water. Water ponding refers to a puddle of water that stays on the roof for more than 48 hours, no matter how small or large. Water ponding might not be alarming until it becomes a regular issue, destroying your roofing membrane and causing water damage to the building. Although having spray foam roofing done on your flat commercial roof can limit the damage to your roof, having a proper drainage system is still a good idea.

Here are some of the negative effects of Water Ponding-

  • Small pools of standing water on your roof can become breeding sites for mosquitoes. More standing water means more mosquitoes, which can bother building occupants and potentially spread disease.
  • Standing water can promote the growth of algae and even larger plants, which makes cleaning drains harder and can lead to clogs.
  • Fungus thrives in wet conditions and may grow in standing water, potentially damaging roofing materials.
  • Birds often nest on rooftops, but standing water can attract them to drink there instead. Reducing the appeal of your roof to birds is a wise move that can help prevent damage.

Types Of Commercial Flat Roofs Drainage Systems

A fully functioning drainage system can completely dry out your roof within two days of the rain stopping. If that does not happen, something is wrong with your drainage system, and you will need professional help to inspect it and get it fixed. With that being said, let’s take a look at some of the most common drainage systems for your flat commercial roof.


Gutters are commonly used to drain rainwater from sloped and flat roofs. These drainage systems are installed on one side of the roof and slope in a specific direction to direct water away from the building, thus helping to prevent water damage.

However, gutter drainage systems have some disadvantages. As time passes, gutters can pull away from fascia boards, which connect the gutter system to the building. Additionally, gutters and downspouts need regular maintenance to avoid clogging with debris.


Scuppers differ from gutters as they are installed in various roof areas to direct water away. Positioned at low points on the roof, scuppers have large square openings on the outer wall that allow water to flow out and down the side of the building.

Roof crickets and triangular structures help channel water toward the scuppers for effective drainage. Scuppers are architecturally appealing and cost-efficient and require less maintenance, although they may need regular cleaning, like gutter downspouts.

3.Interior Drains

The third drainage option for flat roofs involves an internal system of pipes. These pipes are installed at sloped areas of the roof to carry water away to the sewer. This type of drainage system drains water similarly to how a sink drains water.

Protected within the roof and walls, these pipes are less likely to burst, crack, or freeze. The main drawback is that interior drains are the most expensive option, needing professional installation and regular maintenance to ensure the pipes are clear.

Key Takeaway

As you know, without a proper drainage system on your roof, you will face water ponding and water collection, which can lead to structural damage to your building. Even if you have a roof drainage system in place, it will require regular maintenance with the help of a professional to avoid water ponding during the rainy season. So we have come up with another solution to avoid water damage.

The one-stop solution to avoid water damage is spray foaming your roof. Spray Foaming your roof in Redding not only protects your roof from water damage but also protects your flat roof from UV damage, which is a big enemy of flat roofs. Overall, applying polyurethane foam to your roof can add an extra layer of protection and insulation, significantly reducing the risk of water damage.

Protect Your Commercial Flat Roof with Foam Roofing in Redding

Our expert team in Redding ensures your roof remains watertight and efficient with Spray foam roofing. Foam Experts Co. offers spray foam roofing services to improve your commercial roof’s durability and energy efficiency. You can now say goodbye to frequent water ponding and the problems associated with it – like mosquitoes, algae, and structural damage. You will not only have a leakproof roof but the roof will last longer than usual.

Contact Foam Experts Co. today for a consultation. Let us show you how our foam spray solutions can keep your commercial building dry and protected from the elements. Don’t wait protect your roof with the best in the business!