Home Home Repair Tips for Evaluating Roof and Flashing Leaks

Tips for Evaluating Roof and Flashing Leaks


If you have ever had a roof leak you know how frustrating it can be to try and find the source of the leak. More often than not you will find that the leak is due to a problem with flashing. As you can see in the photo, flashing problems (usually due to improper installation) can cause serious damage. Unfortunately, this damage is often hidden until it becomes severe. In this article I’ve asked Michael Chotiner who works for Home Depot to weigh in on some summarized tips to consider when inspecting asphalt shingle roofs for leaks.

Joints between the roof deck and any feature that changes or interrupts the roof slope need flashing. A large majority of roof leaks are caused by missing, improperly installed or failed flashing in the following areas:

The most effective protection for joints where a chimney passes through a roof deck are joints crafted with sheet metal step flashing. There are a number of good ways to construct chimney flashing, and all require skilled craftsmanship. But even the best are vulnerable to weathering, freeze-thaw cycles, normal expansion and contraction caused by temperature fluctuations, and settling or sagging of a house foundation and roof structure. If you see evidence that a leak has its origin from a point high up on a roof-that is, if water stains appear on ceilings well away from exterior walls-suspect the chimney flashing. A chimney flashing probably needs replacement or repair if:

  • Visible metal is bent or twisted;
  • The sheet metal isn’t in continuous contact with the chimney;
  • There are signs of rust or other oxidation;
  • Roof cement or caulk has been applied over the metal flashing, especially if it’s dried and/or cracked;
  • If you find loose brick or bad mortar joints in a masonry chimney, they may also be the source of leaks.

Vent Stacks:
Plumbing vents that come up through a roof deck should be protected with sheet metal / rubber boot flashing with a bead of roof cement applied at the top joint where the flashing meets the pipe. The source of a leak could be around the vent stack penetrating the roof if: