Have you checked your existing roof drains lately? If not, you could be headed for big trouble. If you’re retrofitting your roof or installing a new one, do you know enough about roof drainage systems to maximize roof performance and longevity? Read on to learn more about this critical topic.
Why are roof drains so critical?
Bad roof drains spell trouble with a capital T. Ask any commercial landlord or property manager about leaks caused by poor drainage and you’re likely to hear horror stories about leaks leading to ruined insulation, interior and external damage, structural problems and even premature roof replacement—all at a heavy cost.
You can be better prepared to sidestep the consequences of poor roof drainage by understanding why proper drainage is so crucial and knowing how to battle common roof drain issues.
Read part one in our series: Advantages and Disadvantages of Interior versus External Roof Drainage: What You Need to Know
What do your roof drains do?
Roof drains are all about managing water. The concept is easy. The drainage system is responsible for evacuating water from the roof and keeping it from infiltrating the structure. For owners of low-slope or flat roof buildings often found in commercial and industrial structures, water ponding is a particular concern.
Flat roof drainage and water ponding Â
Ponding water is a telltale sign of poor drainage that can lead to leaks. All else being equal, any breach of the roof membrane will lead to more serious leaks. Ponding water happens when rain collects in dips and uneven roof surfaces. In normal sunlight, water should not remain on a roof for more than 72 hours after a rainstorm. The National Roofing Contractor’s Association (NRCA) considers ponding to be when water remains on the roof 48 hours after a rainfall.
Occasional puddles aren’t likely to create problems, but regular water ponding can cause serious roof leaks and damage. Potential consequences include damage to roofing materials and membranes, components such as trusses, equipment on the roof, and even structural integrity. Ponding can also encourage vegetative growth, provide a haven for wildlife, and lead to insect infestations. Making matters worse, it’s more difficult to complete repairs in or near pooling water, especially in wintertime.
Drainage and the freeze/thaw cycle
Ponding water is always a major concern, but not the only one. In Toronto, the freeze-thaw cycle adds a layer of risk that roofers must consider when planning drainage systems. For example, excess water can crack drainage components, disconnect gutter sections and more.
Signs of potential roof drain issues Â
Be on the lookout for the following signs that your drainage system needs attention:Â
- Standing water on the roof after a rain event Â
- Excessive vegetation on the roof
- Water stains on ceilings or walls inside the building  Â
- A musty odour or visible mould growth
- Visibly broken, clogged or misaligned gutters and downspouts  Â
- Soil erosion around the building’s foundation  Â
- Bubbles or blisters on the roof membrane  Â
- Cracks or damage around roof drains
- Condensation or excess moisture and humidity
- A damaged or sagging roof membrane
 If you notice any of these issues, promptly contact a qualified roofing contractor to assess the situation and schedule necessary repairs. While some damage is gradual, it’s smart to hire a contractor with 24/7 emergency services.
Roof drainage design considerations
If you are installing a new roof, modifying one, or considering a retrofit, what type of roof drainage systems should you consider? There is no right or wrong answer. The best advice would be to work with your roofer to discuss all the relevant factors, including structural considerations, industry and building usage, the surrounding environment, climate and wind conditions, building codes, the age and lifespan of the roof and your budget.
 Based on your needs and budget, the roofer will recommend one of the following types of roof drain systems.
- Internal roof drainage: In this type of system, drains from the roof lead to an internal system of pipes. Design and installation complexity results in higher initial costs, but maintenance costs over time may be lower.
- External roof drainage: Water is drained away from the roof using gutters, scuppers and downspouts on the building’s exterior. While less expensive, exposure to the elements may increase maintenance costs.
- Green roofs: This eco-friendly solution drains water through vegetation and a growing medium and then flows through filtration and drainage layers, with an overflow system to collect and remove excess water.
Decision-making will include a cost-benefit analysis in consultation with the roofer. Budgeting must factor in initial versus long-term costs, including roof performance, maintenance costs and longevity. For example, paying for premium quality materials and superior workmanship may cost more, but the roof will likely perform better and last longer.
7 ways to protect your roof drainage systems
It pays to take all precautions against water ponding, the freeze-thaw cycle and other water-related risks with proper drainage design and installation, ongoing maintenance, prompt repairs and twice-yearly roof inspections.
Here are 7 tips to avoid the consequences of poor roof drainage:Â
- Plan for regular visual inspections and routine maintenance of drainage systems.
- Clear debris and organic material from drains after storms.
- Schedule twice-yearly roof inspections to check for missing, damaged, disconnected drainage components or other hidden issues beneath the roof’s surface.
- Quickly notify your roofer if you see any signs of potential drainage issues.
- Make repairs promptly so small problems don’t become big ones.
- Make sure any rains that discharge to grade are not a slip-and-fall hazard in winter months.
- Talk to your contractor about drainage if you are planning roof modifications.
Be proactive about roof drainage
No matter the type of roof drainage you choose, don’t let leaks and drainage issues slide. Failure to protect against roof drainage problems can lead to poor roof performance, premature roof aging, higher maintenance costs and even structural damage. Also at risk are your roof warranty protections and insurance coverages.
 Look for a roofer known for following industry best practices, meeting manufacturers’ guidelines and complying with local building codes. Also, while many roof issues come on gradually, some are sudden. Hire a roofing company that responds quickly to service requests and offers 24/7 emergency repair capabilities. Â
The importance of a trustworthy roofing partner
Avoid the risks associated with poor roof drainage. Protect your investment by hiring a reputable roofing company with the experience to make sound recommendations, accurately evaluate your drainage needs, design an effective system and use high-quality materials.
Since 1956, Elite Roofing in Toronto has been a trusted commercial and industrial roofing partner, with our superior workmanship backed by our rapid-response 24/7 emergency repair services. Get the Elite Advantage.
