Chimneys are a common feature on many older homes in Toronto, including those with flat roofs. While they add charm and serve functional heating purposes, chimneys can also become a major source of roof leaks—especially when their flashing begins to fail. Chimney flashing repair is one of the most critical aspects of flat roof maintenance and should never be overlooked by property owners.
Flashing is the material that seals the gap where the chimney meets the flat roofing membrane. On sloped roofs, water naturally flows down and away, but on flat roofs, water can pool around the base of the chimney for hours—or even days—after rain or snow. If the flashing is damaged, improperly installed, or deteriorating with age, this standing water has direct access into your building’s interior.
One of the most common problems is separation between the flashing and the masonry. Over time, brick chimneys expand and contract with temperature changes. If the flashing wasn’t installed with flexibility in mind, it can crack or pull away from the brick, creating an open seam. Older mortar joints and crumbling brick only make the problem worse, allowing water to travel between the chimney and roof structure.
Rust and corrosion are also red flags. Many older flat roofs in Toronto still use metal flashing that hasn’t been replaced in decades. Once it starts to rust, the metal weakens and eventually allows water to seep underneath. This kind of slow leak is dangerous—it may not be visible until damage inside the walls or attic becomes serious.
Another issue is improper slope or pooling around the chimney. If water sits against the chimney base due to a sunken roof area or poor drainage, it will continually stress the flashing, weakening the seal. Over time, the roofing membrane around the chimney can also blister or crack under pressure.
The first step in chimney flashing repair is a detailed inspection by a flat roofing expert. They’ll assess the flashing, masonry joints, membrane condition, and drainage slope around the chimney. If damage is minimal, re-sealing or reinforcing the existing flashing may be enough. In more advanced cases, partial removal and full replacement of flashing may be necessary—especially if the chimney base or membrane has begun to fail.
To prevent flashing failure in the future, regular inspections are essential. Toronto homeowners should check chimney flashing at least once a year, ideally after winter. Keep the area free of debris, monitor brick condition, and look for signs of rust or uplift.
If you’ve noticed interior leaks near your chimney or discoloration on walls and ceilings, don’t wait. For professional flat roof repair Toronto, contact Flat Roof Repair Toronto. Their team also provides expert flat roof flashing repair and residential flat roof repair to protect your home from chimney-related leaks.
