While Toronto winters bring snow and ice, summer creates a different set of challenges for flat roofs—especially when it comes to heat. Intense sun exposure, rising temperatures, and UV radiation can silently wear down roofing materials over time. If you notice blisters, cracks, or unusual surface changes during the warmer months, it could be a sign your flat roof is suffering from heat damage.
Flat roofs absorb more heat than sloped roofs because they have a larger surface area exposed directly to the sun. On a hot summer day in Toronto, the temperature on the roof surface can reach well above 60°C. This constant heat causes roofing membranes—especially older ones made of asphalt or modified bitumen—to expand and soften. When they cool down at night, they contract. Over time, this daily cycle of expansion and contraction causes the materials to crack or lose adhesion.
One of the most common signs of summer heat damage is blistering. These are raised bubbles on the membrane surface, often filled with air or moisture. Blisters occur when trapped moisture or air expands under intense heat. While small blisters may not leak immediately, they weaken the membrane and often burst under foot traffic or after rain, leading to serious leaks.
Another concern is UV degradation. Prolonged exposure to sunlight breaks down the chemical structure of the roofing material, causing it to become brittle, chalky, or discolored. This process is especially common on older flat roofs that haven’t been coated or protected with UV-resistant materials.
Seams and flashing are also affected by summer heat. As materials expand and contract, they pull away from seams, joints, and roof penetrations. Even small separations around vents, drains, or skylights can allow water in once a summer thunderstorm hits.
If your flat roof is exposed to rooftop equipment like HVAC systems or solar panels, it may also experience localized heat stress. These units can radiate additional heat onto the membrane, accelerating wear and increasing the risk of membrane failure in those areas.
To prevent heat damage, consider installing reflective roof coatings or upgrading to a light-colored roofing system that reflects rather than absorbs heat. These options reduce thermal cycling, lower cooling costs, and extend the roof’s lifespan.
If your roof feels soft underfoot, shows bubbling, or has discolored patches, it may already be suffering from heat damage. For experienced and prompt flat roof repair Toronto, contact Flat Roof Repair Toronto. They also offer expert flat roof repair specialists and residential flat roof repair to handle summer wear and protect your property year-round.