12 Tips for Finding and Fixing Leaks In Your Roof

October 2024 · 3 minute read

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Stop Leaks in Walls and Dormers

Water doesn’t always come in through the shingled surface. Wind-driven rain can seep in from above the roof around windows, between corner boards and siding, and through cracks and knotholes in siding.

Dormer walls provide plenty of opportunity for water to dribble down and seep through the roof. Caulk between the corner boards, window edges, and siding can be old, cracked or missing, allowing water to penetrate and work its way behind the flashing and into the house. Even intact caulk may not fully seal against the adjoining surfaces.

If you suspect leaky caulk, dig it out with a putty knife and replace it with a fresh dose of high-quality caulk. While you’re at it, check the siding above the step flashing at the base of the wall. Replace any cracked, rotted or missing siding, ensuring the new piece overlaps the step flashing by at least two inches.

If you still have a leak, remove the corner boards and check the overlapping flashing at the corner. Often, you’ll find old, hardened caulk that needs to be replaced where the two pieces overlap at the inside corner.

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Control Leaking at Roof Joints

Complex roofs need special attention, especially at joints where one roofline meets another. The roof in this image leaks during the snowy part of winter and during storms in the summer, no doubt because of poor flashing.

The soffit that meets the roof is one of the toughest areas to waterproof, especially when the roof shows signs of an ice dam. O’Brien says that ice dams “are most often caused by improper ventilation and insulation in your attic or by clogged gutters, which allow ice to build up.” Eventually, water pools behind the dam and works its way back up under the shingles and under the soffit until it finds an opening through the roof.

The solution begins with good flashing:

  • Remove the shingles down to the roof decking.
  • Slip a strip of adhesive ice-and-water barrier (available where roofing repair products are sold) under the soffit/main roof joint. Depending on how the roofs join, you may have to cut a slot to work it in far enough. It should overlap another piece of ice-and-water barrier laid below, all the way down to the roof edge. This should cover the most leak-prone areas.
  • Slide metal step flashing behind the fascia board (the trim behind the gutter) in such a way that the valley flashing laid over the joint where the two roofs meet overlaps it by at least two inches.
  • Re-shingle.

    • Improved attic insulation and ventilation are usually the best ways to prevent ice dams, but they might not be effective in this complicated leaky roof situation. If not, consider installing heating cables on that part of the roof.

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    Replace Damaged Step Flashing

    Step flashing prevents leaks at the base of a wall that intersects the roofline. Each short section of flashing channels water over the shingle downhill from it. If the flashing rusts through, or a piece comes loose, water will run right behind it, and go into the house.

    Replace rusted flashing. To get the old flashing out, you have to remove any shingles on top of it and pry the siding loose. Then you can fit new flashing under the siding, affix it to the wall, replace the siding and then replace the shingles. It’s that simple.

    Don’t forget to nail it securely in place, or it will eventually slip down to expose the wall. Check out this article for more on installing your own step flashing.

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