Clues that point to condensation
Condensation forms when humid air meets a surface cold enough for water vapour to become liquid. It often appears across the room-side glass on cold mornings and can be heavier in bedrooms, bathrooms and kitchens.
If moisture appears without rain, reduces as the day warms or improves with ventilation, indoor humidity is likely contributing.
Clues that point to water entry
Moisture that appears during wind-driven rain, begins at one corner, stains nearby plaster or persists inside the wall needs a different response. The source may be the window, the perimeter seal, flashing or another building element above it.
Do not seal over drainage openings or make a cosmetic repair before the water path is understood. Trapping water may make the underlying problem harder to find.
Make the first inspection more useful
Dry the area, photograph the pattern and note the weather, room activity and time of day. That short record gives an installer or building professional much better evidence than a dry window inspected days later.
- Use exhaust fans and short periods of cross-ventilation where practical.
- Keep tracks and intended drainage paths clear.
- Arrange an inspection if moisture is recurrent, damaging finishes or tied to rain.
A final note
This guide is general information, not project-specific technical or regulatory advice. Confirm your requirements with the appropriate qualified professional.