How to Find a Roof Leak?

Generally, it’s better to fix a leaky roof immediately, no matter if it isn’t bothering you or you’re getting a new roof in the next year because unless you make a roof repair early, small leaks (are easily repairable) can turn into serious problems for the home one day. 

So knowing you have a leaky roof is the easy part (water stain on the ceiling, dark streaks, etc.), finding a leak is the hardest part and a roof leak repair is pretty easy too.

Steps to Finding a Roof Leak

To find a leak, there are a few methods that have a decent track-record of finding troublesome roof leaks.

1. Identify General Hints of Water Damage

Matching where the ceiling water stain aligns with the roof uphill, the source of leak could be directly above the ceiling stain, or to the right or to the left of it. A helpful hint is to look at roof penetrations (chimneys, air vents, plumbing, domers, etc.) are a commonplace for leaks to appear as opposed to open areas of the roof, where it is more rare. With that in mind, if you have access to the attic, using a flashlight it’s possible to look for signs of suspicious water damage (mold, dark streaks, dripping, etc.). Which should uncover some clues as to where the leak is coming from, otherwise try the next method.

2. Use Running Water from a Garden Hose to Track Down a Leak

With one person on the roof with a garden hose and another person inside to see if the leak returns. Roughly, spending over an hour, the person on the roof is trying to isolate where the leak is coming from by spending a few minutes running the hose on each of the suspected areas of the roof. It’s recommended to work your way up the roof’s slope, making it easier to rule out areas before moving on. Make sure to instruct the person inside to communicate to you that the leak came back, this allows the other person to know they found the area that is leaking. If this doesn’t uncover some clues as to where the leak is coming from, otherwise try the next method.

3. Process of Elimination: Take Note of Patches of Water Damage

If running water from a garden hose doesn’t reveal the leak, slowly start removing shingles to look for discolored roof felt paper, water stains or rotted wood underneath. Depending on the severity of any of these, try to trace back to which shingle(s) have the worst damage underneath them. Most likely, this is where the leak is. Which should uncover some clues as to where the leak is coming from, otherwise try the next method.

4. Check the Attic Insulation: Identify Water Trapped in Vapor Barriers

If your ceiling has a plastic vapor barrier between the drywall and attic insulation, this barrier normally traps the water that is leaking. Push the insulation aside, looking for water flow stains on the plastic and this water flow stain is most likely to appear near openings like light fixtures.

5. Check the Attic's Roof Underside: Look for Condensation on Nails

If there aren’t any signs of water flow marks on the vapor barrier, look at the underside of the roof for “shiners”. These are nails that were driven in deeply and appear to be frosted; Moisture that escapes into the cold attic from the rooms below often condenses on these cold nails, and on cold nights they freeze, becoming a white colour, and during the day they melt. Causing a drip off of these nails. If that’s the case, then use side-cutting pliers to clip the nail to prevent this from continuing.

Conclusion

Somewhere along the tracking process, a leak should appear evident at some point. 

In the case a roof has multiple layers of shingles, it's best to understand that though a leak has been identified and repaired it will not solve the problem until the entire roof is replaced. Primarily because water will be trapped throughout your roof and will inevitably leak again.

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