Interior paint blistering traced to exterior water entry at a sill
The blistering returned after repainting because the source outside the wall had not been corrected.
✓Contractor Confirmedrecorded confirmation level
01 / OBSERVED
→Blistering paint below a window
02 / CONFIRMED CAUSE
→Water entry at an exterior sill joint
03 / REPAIR
→The sill joint and drainage path were repaired before the wall was dried and redecorated.
04 / VERIFY
The substrate remained dry through later rain and the finish stayed bonded.
WHAT CHANGED THE DIRECTION
The evidence that separated the cause
Supporting clues
- Below one sill
- Worse after rain
- Previous paint-only repair failed
Checks performed
- Exterior detail inspection
- Moisture map
- Rain observation
Field lessonRepair the source before repairing the visible finish.
