Understanding the Importance of Flat Roof Drainage Systems

Drainage Systems
Drainage Systems

As the fireworks lit up the sky last night in celebration of Canada Day, we at NorthCan Roofing hope everyone enjoyed the long weekend. While the vibrant displays of light were a sight to behold, the persistent rain we’ve been experiencing throughout the start of this summer and spring serves as a stark reminder of the importance of proper drainage for our commercial and industrial flat roofs.

With more rain forecasted for this week, ensuring that your flat roof drainage system is functioning optimally is crucial to prevent issues like water pooling, leaks, and potential structural damage. At NorthCan Roofing, we understand the challenges that come with maintaining a flat roof in the Greater Toronto Area’s variable weather conditions. That’s why we’ve put together this comprehensive guide to help you install a reliable commercial flat roof drainage system, ensuring your roof is well-equipped to handle the rainy days ahead.

Understanding the Importance of Flat Roof Drainage Systems

Commercial flat roofs, unlike their pitched counterparts, do not naturally shed water. This makes them particularly susceptible to water accumulation, which can lead to a range of issues such as leaks, structural damage, and premature roof deterioration. An effective drainage system is essential to manage water flow and prevent these potential problems.

Common Drainage Solutions for Flat Roofs:

  1. Internal Roof Drains: These are installed at low points of the roof, allowing water to be funneled into a network of pipes that carry it away from the building. Internal drains are especially effective for large roofs as they minimize water exposure to the exterior walls and foundation.

  2. Scuppers: These are openings in the parapet walls of the roof that allow water to drain directly off the edge. Scuppers are typically used in combination with downspouts or leader pipes to channel water away from the building.

  3. Gutters and Downspouts: Gutters are installed along the edge of the roof to collect water and direct it to downspouts, which carry it to the ground level. This system is common and effective but requires regular maintenance to prevent clogging.

Benefits of a Well-Designed Drainage System:

  • Prevents Water Pooling: Reduces the risk of leaks and water damage.
  • Extends Roof Lifespan: Proper drainage minimizes wear and tear.
  • Protects Building Structure: Reduces the likelihood of water infiltration that can weaken the building’s foundation and walls.
  • Enhances Safety: Prevents ice formation in colder months, which can be hazardous.

Types of Drainage Systems for Commercial Flat Roofs

When it comes to ensuring proper drainage for commercial flat roofs, there are several effective systems to consider. Each type offers unique benefits and is suited to different building requirements. Here’s a closer look at the primary drainage options:

Internal Roof Drains: Efficient and Hidden

What Are Internal Roof Drains? Internal roof drains are strategically placed at the lowest points of the roof to capture water and direct it into a network of pipes inside the building. These pipes then carry the water away, minimizing exposure to the building’s exterior.

Benefits of Internal Roof Drains:

  • Discreet and Aesthetic: Hidden from view, maintaining the roof’s appearance.
  • Effective Water Management: Efficiently handles large volumes of water, reducing the risk of leaks and damage.
  • Protection for Building Structure: Keeps water away from exterior walls and foundations.

Scuppers: Simple and Effective

What Are Scuppers? Scuppers are openings in the parapet walls or edges of the roof that allow water to drain directly off the roof’s surface. They are often used in conjunction with downspouts or leader pipes.

Benefits of Scuppers:

  • Cost-Effective Solution: Generally less expensive to install and maintain.
  • Easy Maintenance: Fewer components and simple design make them easy to clean and inspect.
  • Reliable in Heavy Rainfall: Capable of handling large volumes of water quickly.

Gutters and Downspouts: Traditional and Reliable

What Are Gutters and Downspouts? Gutters are channels installed along the edges of the roof that collect and direct water to downspouts, which then carry the water safely away from the building.

Benefits of Gutters and Downspouts:

  • Wide Availability: Common and easy to find in various materials and styles.
  • Effective Water Redirection: Efficiently channels water away from the roof and foundation.
  • Versatile Application: Suitable for various types of flat roofs and building designs.

Materials and Tools Needed for Installation

Before beginning the installation of a flat roof drainage system, it’s essential to gather the necessary materials and tools. Proper preparation ensures a smoother installation process and helps avoid potential issues.

Essential Materials for Flat Roof Drainage Installation

  • Drains, Scuppers, and Gutters: Depending on the chosen system, ensure you have the appropriate components.
  • Pipes and Downspouts: For directing water from drains and scuppers.
  • Sealants and Flashing: To create watertight seals around drainage components.
  • Fasteners and Supports: Screws, brackets, and other hardware to secure the system.

Tools Required for a Successful Installation

  • Drill and Saw: For creating openings and securing components.
  • Measuring Tape and Level: To ensure accurate placement and alignment.
  • Safety Gear: Gloves, goggles, and harnesses for safe working conditions.
  • Roofing Tools: Trowels, rollers, and brushes for applying sealants and adhesives.

Preparing the Roof for Drainage Installation

Proper preparation is critical for the successful installation of a flat roof drainage system. This step ensures that the roof is ready to accommodate the new components and function optimally.

Inspecting the Roof for Existing Damage

  • Check for Leaks and Weak Spots: Identify and repair any current issues to prevent future problems.
  • Assess Structural Integrity: Ensure the roof can support the new drainage components.

Cleaning the Roof Surface

  • Remove Debris and Dirt: Clear the roof of any debris, dirt, or leaves that could obstruct drainage.
  • Clean Around Installation Areas: Ensure the areas where drains, scuppers, or gutters will be installed are clean and dry.

Measuring and Marking the Locations

  • Plan Drainage Points: Identify the best locations for drains or scuppers based on roof slope and structure.
  • Mark Installation Sites: Use chalk or markers to outline where each component will be installed.

Step-by-Step Installation Guide

Installing a commercial flat roof drainage system involves several precise steps to ensure effective water management. Here’s a detailed, step-by-step guide to help you through the process.

Step 1: Installing Internal Roof Drains

Drilling Holes for the Drains

  • Locate Optimal Drain Points: Identify the lowest points on the roof where water naturally collects.
  • Drill Appropriately Sized Holes: Use a drill to create holes that match the size of your drain components.

Placing and Securing the Drain Body

  • Insert Drain Bodies: Fit the drain bodies into the drilled holes, ensuring they sit flush with the roof surface.
  • Secure with Fasteners: Use screws or bolts to secure the drains firmly in place.

Connecting Drain Pipes to the Plumbing System

  • Attach Pipes to Drains: Connect the drain bodies to the drainage pipes.
  • Ensure Proper Slope: Make sure the pipes slope downward to facilitate water flow to the exit points.

Sealing Around the Drain to Prevent Leaks

  • Apply Sealant: Use a high-quality waterproof sealant around the drain bodies.
  • Install Flashing: Add flashing around the drains to provide an additional layer of protection against leaks.

Step 2: Installing Scuppers

Cutting Openings in the Parapet Walls

  • Measure and Mark Locations: Determine where the scuppers will be placed and mark these points on the parapet walls.
  • Cut Openings: Use a saw to cut the marked areas, creating openings for the scuppers.

Fitting and Securing Scuppers in Place

  • Insert Scuppers: Place the scuppers into the cut openings, ensuring they fit snugly.
  • Secure with Fasteners: Use screws or bolts to hold the scuppers firmly in place.

Attaching Downspouts or Leader Pipes

  • Connect Downspouts: Attach downspouts or leader pipes to the scuppers to direct water away from the building.
  • Ensure Secure Connections: Make sure all connections are tight to prevent leaks.

Sealing Around the Scuppers to Prevent Leaks

  • Apply Waterproof Sealant: Seal around the edges of the scuppers with waterproof sealant.
  • Install Flashing: Add flashing around the scuppers for additional leak protection.

Step 3: Installing Gutters and Downspouts

Measuring and Cutting Gutter Sections

  • Measure Roof Edges: Measure the lengths of the roof edges where gutters will be installed.
  • Cut Gutters to Size: Use a saw to cut the gutter sections to the appropriate lengths.

Attaching Gutters to the Roof Edge

  • Position Gutters: Place the gutters along the roof edge.
  • Secure with Brackets: Use brackets and screws to attach the gutters to the roof.

Connecting Downspouts to Gutters

  • Attach Downspouts: Connect downspouts to the gutters, ensuring a tight fit.
  • Secure Downspouts: Fasten the downspouts to the building with straps or brackets.

Ensuring Proper Slope for Water Flow

  • Check Gutter Slope: Ensure the gutters are installed with a slight slope towards the downspouts.
  • Adjust as Needed: Make any necessary adjustments to maintain the correct slope for efficient water drainage.

Testing and Ensuring Proper Functionality

After installing the drainage system, it’s crucial to test it thoroughly to ensure everything functions correctly and efficiently.

Checking for Leaks and Making Necessary Adjustments

  • Inspect All Seals: Check all seals around drains, scuppers, and gutters for potential leaks.
  • Apply Additional Sealant: If any leaks are found, apply more sealant to fix them.

Ensuring Water Flows Correctly Through the System

  • Test with Water: Pour water onto the roof and observe its flow through the drainage system.
  • Check for Obstructions: Ensure there are no blockages preventing water from flowing freely.

Making Final Inspections and Adjustments

  • Inspect All Components: Conduct a final inspection of all drainage components.
  • Tighten Connections: Ensure all screws, bolts, and connections are secure.
  • Adjust as Necessary: Make any final adjustments to optimize the system’s performance.

Maintenance Tips for Flat Roof Drainage Systems

Maintaining your flat roof drainage system is essential to ensure its long-term functionality and to prevent future problems.

Regular Inspection Schedules

  • Monthly Checks: Inspect the drainage system monthly, especially during rainy seasons.
  • Post-Storm Inspections: Check for any damage or blockages after heavy storms.

Cleaning Debris from Drains, Scuppers, and Gutters

  • Remove Leaves and Debris: Regularly clear leaves, dirt, and debris from drains, scuppers, and gutters.
  • Use Proper Tools: Employ tools like gutter scoops and brushes to clean hard-to-reach areas.

Addressing Any Issues Promptly to Prevent Damage

  • Fix Leaks Immediately: Repair any leaks as soon as they are detected.
  • Replace Damaged Components: Promptly replace any damaged or worn-out parts of the drainage system.

Common Mistakes to Avoid During Installation

Avoiding common mistakes during the installation of your drainage system can save time, money, and future headaches.

Incorrect Placement of Drains or Scuppers

  • Proper Planning: Ensure you plan the placement of drains and scuppers correctly to maximize efficiency.
  • Consider Roof Slope: Place components where water naturally collects.

Insufficient Sealing Around Components

  • Use High-Quality Sealants: Invest in high-quality sealants for better protection.
  • Double-Check Seals: Always double-check seals around all components.

Ignoring the Slope for Proper Water Flow

  • Maintain Proper Angles: Ensure gutters and pipes are installed with the correct slope.
  • Adjust as Needed: Regularly check and adjust the slope to maintain optimal water flow.

Why NorthCan Roofing is Your Best Bet for Flat Roof Drainage Solutions

Choosing the right partner for your commercial flat roof drainage system is crucial to ensuring the longevity and durability of your roof. At NorthCan Roofing, we specialize in providing top-notch roofing solutions tailored to meet the unique needs of businesses in the Greater Toronto Area.

Expertise and Experience

With years of experience in the commercial and industrial roofing industry, NorthCan Roofing has the knowledge and expertise to handle any drainage challenge. Our team of certified professionals is trained to install and maintain a variety of drainage systems, ensuring your roof is protected against the elements.

High-Quality Materials and Workmanship

We use only the highest quality materials and state-of-the-art techniques to ensure your drainage system is durable and efficient. Our commitment to excellence means you can trust that your investment is in good hands.

Comprehensive Services

From initial inspection and planning to installation and ongoing maintenance, NorthCan Roofing offers a full range of services to keep your roof in optimal condition. We tailor our solutions to your specific needs, providing customized drainage systems that fit your building’s requirements.

Customer Satisfaction

At NorthCan Roofing, customer satisfaction is our top priority. We work closely with our clients to ensure their needs are met and their expectations exceeded. Our dedication to quality and service has earned us a reputation as a trusted partner in the roofing industry.


Proper drainage is essential for maintaining the health and longevity of your commercial flat roof. By following our comprehensive guide, you can ensure that your roof drainage system is installed correctly and functions efficiently, protecting your building from water damage and extending the life of your roof.

When it comes to expert installation and maintenance of flat roof drainage systems, NorthCan Roofing is your best choice. Our experienced team, high-quality materials, and commitment to customer satisfaction make us the ideal partner for all your commercial roofing needs. Contact us today to learn more about how we can help you keep your roof in top condition, no matter the weather.

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