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  • Writer's pictureElite Roofing

How to Drain Water from a Flat Roof: A Guide for Business Owners

Proper drainage is crucial for the longevity of flat roofs, a common architectural feature in commercial buildings. Poor drainage can lead to water buildup, causing structural damage and potentially costly repairs. As a business owner, understanding how to efficiently remove water from your flat roof is key to protecting your investment. In this guide, we'll navigate through the considerations and practical steps for ensuring effective flat roof drainage.


Understanding Flat Roof Drainage Systems

Flat roofs are not entirely flat; they have a slight pitch to facilitate water drainage. However, this subtle gradient needs a proficient drainage system to function correctly. Common types of flat roof drainage systems include:


  • Interior Drains: Located at the center of the roof, resembling indoor floor drains. Pipes connected to these carry water away and underground, out of sight.

  • Scuppers: Openings on the sides of the roof that allow water to drain off the edges.

  • Gutters and Downspouts: Channels along the roof edge that guide water down from the roof.

A well-designed drainage system prevents standing water, thereby reducing the risk of leaks and weight strain on the building's structure. When planning or inspecting your drainage system, consider local climate conditions, the size of your roof, and your building’s specific design elements.


Identifying Drainage Issues

Regular monitoring of your flat roof can prevent minor issues from escalating into major problems. Signs of poor drainage include:

  • Pools of water remaining on the roof 48 hours after rainfall

  • Sagging roof sections

  • Visible damage to the drainage components

  • Blocked scuppers or downspouts

Left unaddressed, these issues can lead to leaks inside the building, mold growth, or even roof collapse.

Steps to Drain Water from a Flat Roof

1. Clearing Debris

Debris such as leaves, twigs, and dirt can clog drains, creating water dams on your roof. Regularly remove debris to prevent blockages.

2. Inspecting Drains and Gutters

Check drains, scuppers, and gutters for signs of damage or obstruction. Ensure that they are securely attached and free of cracks or breaks.

3. Assessing Slope and Leveling

An insufficient slope can cause water pooling. Use a level to verify that your roof has the proper pitch towards drainage points. If necessary, adjust the slope.

4. Installing Additional Drainage Components

If your existing system is inadequate, consider adding more drains or widening scuppers to improve flow.

5. Regular Maintenance and Inspection

Schedule routine inspections, especially after severe weather conditions. Immediate attention to small fixes can prevent larger, more expensive issues.

Professional Help and Considerations

If drainage system problems persist or if significant modifications are needed, seek professional help. Qualified contractors can provide expertise that ensures the job meets building codes and maintains the roof's integrity.

When choosing a contractor, consider their experience with commercial roofing, references, licensing, and insurance.


Ignoring flat roof drainage can lead to water damage, structural issues, and hefty repair bills. By taking proactive measures such as routine cleanings, inspections, and engaging professionals when necessary, you protect the value of your property. Remember the impact of regular maintenance on your roof's health and, consequently, on your business. Keep your operations running smoothly by keeping water off your flat roof.



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