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

July 4, 2024

A commercial roof’s main role is to protect the building from harsh weather, like the heat of the sun and heavy rain. But what keeps the roof itself safe from damage, especially water damage?

Unlike residential homes with slanted roofs, which usually don’t have problems with standing water, flat roofs need extra help. Slanted roofs naturally let water flow off due to gravity and gutters. But what about flat commercial roofs?

These roofs need a special drainage system to get rid of standing water. So, today we’ll discuss the different types of drainage systems used on flat commercial roofs, how they work, and more!

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Why Drainage is Important on a Flat Roof

You can think of water as the worst enemy of commercial flat roofs! And if water sits there for too long, it can cause serious problems! Here are some of the problems we are talking about –

Water Ponding: When rainwater pools on a flat roof, it puts extra stress on the building! Over time, this can cause the roof deck to sag or even collapse.
Leaks Inside the Building: Water can seep through the roof, damaging ceilings, walls, and furniture inside the commercial building.
Mold and Mildew: Mold and mildew love to stay in places with moisture, and this can affect indoor air quality and cause health issues like breathing problems, allergies, etc.
Structural Damage: Over time, water can weaken the roof and supporting structure, and repairing it can cost a lot.
Algae and Plant Growth: Algae and plants love to grow in places with standing water! And they can clog drains and make maintenance more difficult.
Mosquitoes: Small pools on the roof can attract mosquitoes, which can bother building occupants and even spread diseases.

How Different Drainage Systems Work on Commercial Flat Roofs

Flat commercial roofs use different methods to move water off the surface. And the mechanisms often vary depending on the drainage system.

Gutters

These drainage systems are installed on one side of the roof, and they slope in a specific direction to move water away from the building, thus helping to prevent water damage. These are great for larger roofs but need regular cleaning to prevent clogs. Plus, over time, gutters can start to come loose from the boards that hold them to the building.

Scuppers

These are openings along the edges of a flat roof that let water drain off. Water flows through the scuppers into the downspouts outside the building. They are simple to check and keep clean, and also easy to maintain.

Interior Drains

These pipes are installed in 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. They work well for larger flat roofs and handle a lot of water efficiently, but they need regular cleaning to avoid clogs.

Siphonic Systems

These are advanced systems that use a vacuum effect to pull water off the roof quickly. They can handle large amounts of water at once. You might see that siphonic systems are usually installed on very large commercial roofs.

All these drainage systems work the same way – they collect water, guide it to exit points, and carry it safely away from your building!

How the Right Roofing Material Helps Drainage

Having a good drainage system is extremely important. But you also need to take care of several other factors along with this to ensure your drainage system works properly. And one of those factors is – choosing the right roofing material. The roofing material will also be responsible for determining how well water will move off your commercial flat roof.

While some materials can trap water around seams or edges, others can help create a smooth flow of water straight to drains. You might have already heard of materials like –

TPO (Thermoplastic Polyolefin)
EDM (Ethylene Propylene Diene Monomer)
PVC roofing membranes

But if you’re looking for something that’ll help your drainage system and its long-term performance, you can use Spray Polyurethane Foam (SPF) roofing! It’s a liquid made of two components – polyol and isocyanate.

When spray foam is applied directly to your roof, it hardens into an insulating layer, reducing energy bills and making it one of the best solutions for flat roof leak repair. It’ll create a smooth surface that can naturally guide water towards scuppers, drains, or gutters and prevent future leaks as well!

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How To Maintain Your Commercial Flat Roof?

Even the best drainage system won’t work properly if you don’t take care of it regularly. So, here’s how you can do that!

Clean drains often: Remove leaves, dirt, and other debris so water can flow freely.
Check scuppers and gutters: Make sure nothing is blocking the water path (check at least once or twice a month).
Watch for ponding: If small puddles stay for more than 24 hours, call a professional who provides commercial roof repair solutions by checking your roof for damage and suggesting necessary repairs.
Call the pros: You need to hire reputable roof repair experts to solve your minor or major roof problems right away to prevent bigger issues in the future.

Common Questions on Commercial Flat Roof Drainage Systems

Why does my flat roof need a drainage system if it barely rains?

Even with little rain, a flat roof needs drainage because water can still collect and cause damage. But if you add a protective layer of spray foam on the roof, you don’t have to worry about rain, sun, or even roof aging, as this renewable roofing solution protects your roof from all kinds of damage.

How long does spray foam roofing last on a flat roof?

With proper maintenance, spray foam roofing can last for more than 30 years!

Are internal drains more expensive than gutters or scuppers?

Usually, yes. But internal drains can handle a larger amount of water and look cleaner. And when they are paired with spray foam roofing, they work even better by preventing ponding water and directing the water into the drains properly.

Call Us Now to Repair Your Commercial Roof!

Takeaway

If you own a commercial property with a flat roof, you need to ensure the drainage system works properly at all times. You can install systems like gutters, scuppers, interior drains, and siphonic setups to collect and move water away safely.

And if you pair these with quality materials, like spray foam roofing, it’ll create a smooth, insulated surface that’ll improve drainage, prevent leaks, and even lower your energy bills!