What the pattern can mean
Water at a window corner can enter through head flashing, cladding joints, sill drainage, frame seals or nearby wall defects. Surface caulk is only one layer.
Why timing matters
Typical trigger: Rain from one direction and pressure against the facade.
Wind pressure drives water behind exterior layers, where it can travel to a frame corner or sill.
Evidence that increases the fit
- One wind direction repeats the leak
- The first wet edge is at the head or side
- Exterior drainage details are missing or blocked
Evidence that weakens it
- The symptom follows indoor condensation
- The leak appears with plumbing use
- Comparable storms from the same direction stay dry
Safe first checks
- Record wind direction and first wet point
- Photograph exterior joints from ground level
- Check whether sill drainage openings are blocked
Important boundary
Do not caulk drainage openings or seal every cladding joint.
Professional handoff: A window or envelope professional should inspect layered flashing and drainage.
Primary references for this topic family
These references ground the general building-science or safety context. They do not diagnose a specific house, replace local requirements or certify a repair.
US Environmental Protection Agency · government guidanceMoisture Control Guidance for Building Design, Construction and MaintenanceMoisture sources, transport, design, construction and maintenance controls.Verified 2026-07-20 · review due 2027-01-20Open source ↗US Department of Energy · government research libraryBuilding America Publications and Solution CenterBuilding enclosure, HVAC, windows, indoor air and high-performance housing research.Verified 2026-07-20 · review due 2027-01-20Open source ↗
Observe→Compare triggers→Repair source→Verify outcome
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