Fix a Leaking Eavestrough Corner in Ottawa

Leaking eavestrough corners — where two runs meet at an inside or outside mitre — are one of the most common repair needs on Ottawa homes, and the good news is that a corner leak is absolutely fixable without replacing the entire eavestrough run. Corners are the highest-stress point in any gutter system because they join two pieces of metal at an angle, creating a seam that must withstand water pressure, thermal expansion, and the weight of debris, snow, and ice. Ottawa's 65-degree annual temperature swing works on that seam relentlessly, and after 10 to 15 years, even well-installed corners often start to leak.

Before attempting the repair, inspect the corner from a ladder on a dry day. You are looking for three things: visible gaps in the sealant line along the inside of the mitre joint, corrosion or pitting around the seam area, and whether the two sections have shifted apart creating a physical gap in the metal. If the gap is less than about 3 millimetres and the metal itself is sound, a sealant repair will fix the problem. If the metal is corroded through or the sections have separated significantly, you may need a professional to cut out and replace the corner fitting.

The Right Way to Seal a Corner

Timing matters — choose a dry day above 10 degrees Celsius with no rain forecast for at least 48 hours. Sealant needs warmth and dryness to cure properly, which limits this repair to roughly May through October in Ottawa. Gather your materials: gutter-specific sealant (not general-purpose silicone — use products like Geocel Gutter Seal or DAP Gutter & Flashing Sealant that are formulated for metal-to-metal adhesion and remain flexible through freeze-thaw cycles), a stiff wire brush, rubbing alcohol, fine sandpaper (120 grit), and work gloves.

Start by clearing all debris from the corner area and at least 12 inches along each run leading into the corner. Use the wire brush to scrape away all old sealant — every bit of it. Old, failed sealant prevents new sealant from bonding to the metal surface, and this is the step most people rush through. Sand the cleaned area lightly with 120-grit sandpaper to create a slightly roughened surface for better adhesion, then wipe everything clean with rubbing alcohol and allow it to dry completely.

Apply a thick, continuous bead of gutter sealant along the entire interior seam of the corner joint, pressing firmly into the gap. Use a gloved finger or small putty knife to smooth the sealant into full contact with both metal surfaces, extending coverage at least one inch beyond the seam on all sides. For outside corners that are exposed to direct water flow, apply sealant on both the inside and outside of the joint. For added durability on persistently leaky corners, apply a gutter repair patch — a piece of aluminum flashing cut slightly larger than the joint area, embedded into a bed of gutter sealant and pressed flat. This creates a waterproof membrane over the seam that outlasts sealant alone.

A properly executed corner sealant repair costs under $25 in materials and lasts 5 to 10 years before needing reapplication. Professional corner repair in Ottawa runs $100 to $250 per corner, which is worth considering for second-storey corners or complex rooflines where ladder work is risky. If your home has multiple leaking corners or the metal at the joint has corroded through, a professional can replace individual corner fittings without touching the straight runs — the Ottawa Construction Network directory at justynrookcontracting.com lists eavestrough contractors experienced in targeted repairs throughout Ottawa.