Short Answer
Different weather conditions expose different weaknesses. Leaks can appear only during wind-driven rain, heavy rain, specific wind directions, snow, freeze/thaw cycles, prolonged rain, or ice-damming conditions. This is why leak diagnosis can require understanding roof geometry and water pathways rather than simply looking for the closest damaged shingle.
Detailed Explanation
A roof that leaks only during certain conditions is telling you something specific about where the weakness is. Wind-driven rain from a particular direction can force water under flashing that would normally shed water fine. Heavy, prolonged rain can overwhelm a valley or gutter that handles normal rainfall. Snow and ice can create ice dams that force water backward under shingles. A leak that only happens during storms from the northeast, for example, might point to a specific roof-to-wall transition or chimney flashing on that side of the house. Understanding the weather conditions that trigger the leak is a critical clue in diagnosing the source.
Why It Matters
The weather pattern that triggers a leak is a diagnostic clue that helps identify the specific failure point, leading to a more effective repair.
Common Mistakes
- ✕Assuming all leaks come from the same source
- ✕Looking only at the area directly above the visible stain
- ✕Ignoring the wind direction and rain intensity during the leak event
Questions to Ask Your Contractor
- ?What direction was the wind blowing during the storm?
- ?Was it heavy rain or wind-driven rain?
- ?How long did the rain last before the leak appeared?
- ?Does the leak happen every time it rains, or only during certain conditions?