Wind-driven rain passes a flashing interface

Rain pressure and direction expose a roof or wall junction that remains dry during calm vertical rain.

Failure path

• Step 1: Wind redirects rain upslope or sideways.
• Step 2: Water reaches a vulnerable flashing edge.
• Step 3: It follows underlayment, framing or fasteners.
• Step 4: The visible stain appears away from the entry point.
• Step 5: Dry weather can hide the active route.

What makes this pathway plausible

The timing, location and operating or weather trigger should repeat. A diagram shows a mechanism; evidence from the actual house determines whether it applies.

Best next observation

Record the trigger and compare the nearest materials, components and routes before opening finishes or choosing a repair.

Verification after repair

Recreate the original trigger when safe, then confirm the symptom does not return and affected materials are stable or drying.