The phrase “100-year storm” means a rainfall event so large that it statistically has only a one-in-a-hundred (one percent) chance of happening in a given year based on that location’s average annual precipitation. That doesn’t mean, however, that the next 100-year storm won’t hit and cause problems with your commercial roof in 50 years, 10 years, next year, or even tomorrow. Be sure to complete your 100-year storm preparation to stay away from potential problems from arising in your commercial roof.
Where were you on Saturday, August 17 when a monster storm dropped a record 128.3mm of rain at Toronto Pearson Airport and the City of Mississauga was doused with a month’s worth of rain in a few hours? That’s even a higher amount than a one in a hundred-year storm!
How about July 16, when 100mm of rain fell in just three hours? Maybe you were stranded on the flooded Don Valley Parkway. Or, you experienced hours of flight delays or cancellations. You could have been one of the many thousands of Hydro One customers who lost power.
Major storms cause major problems for commercial roofs
July started with a string of storms and torrential rains from the remnants of Hurricane Beryl. Just a week later, the July 16 deluge nearly reached GTA’s official 100-year storm threshold—115mm of rainfall in 24 hours. Add in the August 17 deluge and GTA has experienced four 100-year storms since 2013 (as of August 2024).
Predicted to be the rainiest summer on record–and with massive storms becoming more frequent–commercial building owners are trying to battle extreme weather to avoid hundreds or thousands of dollars in repairs.
100-Year Storm Preparation: Preparing your commercial roof for the new normal
The consequences of poor roof preparation can result in business operations shutting down, interior flooding, and unexpected repair costs and insurance claims. With 100-year storms becoming the new normal, it’s time for landlords to batten down the hatches and prepare for a stormy future with 100-year storm preparation.
Year-round steps to prevent commercial roof storm damage
Commercial building owners can take steps year-round to help keep their roof safe against heavy rainstorms. If you have completed roofing repairs, reroofing, or a roof replacement, post-project preparation is also critical. Here are important ways to protect against damage to one of your property’s most critical and vulnerable assets—the roof.
Twice-annual professional roof inspections
Be proactive by scheduling twice-yearly professional roof inspections. A qualified roof inspector can accurately assess a roof’s condition, detect problems early on, and fix small problems quickly—before they get bigger. You can also ask for recommendations on improvements to avoid leaks, standing water, and other roof risks.
Ongoing roof maintenance and prevention efforts
Keep emergencies at bay with proper maintenance and prevention. Regularly clean out organic debris, algae, and other clogs from the drain baskets that prevents rain water from getting into internal drainpipes. Other steps include cutting back overhanging tree branches, removing clutter or left-behind tools, disposing of abandoned HVAC and other equipment, and checking that working equipment and access panels are secured.
Visual roof and property inspections
Keep up to date with roof repairs of active leaks. Check for loose, damaged, or missing materials. Keep your eyes peeled for issues with the roof surface or membrane, flashing, gutters, downspouts, securements, and other elements that can make your roof vulnerable to leaks. Call your roofer immediately if you spot one of these vulnerabilities.
GTA’s storm effectiveness
Roof drains empty into the city’s underground lines, sometimes discharging water into a culvert or storm pond. Because you can’t control the city’s draining infrastructure, ask your plumbing, mechanical or drain contractor for recommendations that might help you overcome weaknesses in the city’s system. Inspect the property’s drainage system with a plumbing or drain contractor. This is to ensure that there are no issues such as damaged clean out covers on rain water leaders, obstructions or broken underground pipes, and more.
100-Year Storm Preparation: Commercial roof to-do roof items after a major storm
If you’re a commercial building owner, attend to your roof after the storm to identify any damage, document it for insurance, and schedule repairs as soon as possible. This will also prepare you for the next rain event.
Drainage issues
Visually check your roof for damage after a storm. Even if you don’t spot an obvious problem, some important drain components are hidden beneath the surface. If there are issue then it’s a good idea to follow up with a professional roof inspection to check for possible damage and then repair any missing or broken parts. Learn more in our guide on everything you need to know about roof drains.
Hard-to-spot obstructions
It’s common for heavy rains to sweep in debris that can block or create partial drain obstructions. Clogs may not always be immediately visible, so call your roofer to check and clear all parts of drains as needed. It is also important to have your plumbing contractor inspect rain water leaders for potential back fall on the pipes and loose or damaged clean out covers on a regular basis.
Control flow drains and weirs
Control flow drains regulate water flow through the drain, act as an overflow if a blockage prevents normal drainage, and slow the rate of runoff during a large storm. The drain often includes a weir, whose narrow slots can easily become blocked with debris, causing water build-up. A professional contractor can ensure that the weird are clear to ensure proper drainage.
Retrofit roof drains
Reroofing projects may use retrofit drains that are inserted into existing drains that are older. Backflow seals in the retrofit drain allow water to flow in only one direction, preventing leakage from backflow pressure during heavy rainfall. However, this system will fail if the seals on the valve are missing or if the retrofit drain was not installed properly. Always use a highly qualified roofer to ensure that retrofit drains are properly installed.
Alternate drainage solutions
Upon inspection, your roofer may recommend alternate drainage solutions, such as overflow scuppers. You may especially need to consider your options if the building’s drains are prone to backing up or where parapet walls are six inches (152mm) tall or higher. While upgrades may affect your budget, they will likely be much less costly than significant storm damage.
Don’t let storm cause commercial roof problems
Extreme weather isn’t going anywhere, and being proactive is your best protection. Partnering with an expert roofing contractor like Elite Roofing can help ensure you’re ready for the next 100-year storm. Call on us to schedule your next inspection. Should the storm overcome your defenses, also count on us for 24/7/365 rapid-response emergency services. Contact us today and get the Elite Advantage.
