How is a roof leak found?
Leak detection works backward from the stain. Someone checks the attic first, looking at the underside of the deck for dark streaks, wet insulation and daylight. Then they go up on the roof and examine the area uphill from the stain, since water runs down before it drips.
The most common culprits get checked first, such as flashing, vent boots and penetrations. If the source is not clear, a hose test can help. One person sprays small sections while another watches from the attic. It takes patience, because a quick spray across the whole roof proves nothing.
A written note on what was found, with photos, helps you decide next steps. If the leak turns out to be one of many problems, that is a sign to look at roof replacement instead of paying for repeated patches.
