Mould around a window needs attention, but its appearance alone does not tell you why the area is damp. Note where the moisture appears and when it happens. These details help a professional investigate the window or building.
Look at where moisture appears
Water on the room-facing glass can be condensation. Note whether it also collects on the sill or nearby wall. Mist that appears to be between panes is a separate observation; ask the original supplier or a glazing professional to assess it. A photo alone cannot show what needs repairing.
Notice when the area becomes wet
Does it happen on cold mornings, after cooking or showering, or after rain? Record the pattern rather than relying on one photograph. Water appearing after rain may need the window and surrounding building checked. A wet sill alone does not prove a frame fault.
Record changes around the window
Take a photograph of the whole window and a closer view of the affected area. Note peeling paint, stained plaster, damaged timber or a musty smell. Observe only from a safe position. Leave hidden parts and outside seals to someone qualified to assess them.
Note the room's ventilation
Record window or wall vents and extractor fans. Mention anything blocked or not working, as well as recent changes to the room. These details help explain the conditions, but do not establish blame.
Choose the next step
Read our guide to safe first steps before cleaning mould. Arrange a building or damp assessment if water keeps returning, finishes are damaged or the cause is unclear. For mist apparently between sealed panes, speak to a glazing professional or the original supplier.
Questions
Does mould prove the windows were fitted badly?
No. An assessment should consider condensation, ventilation and possible water entry. The appearance alone cannot establish the cause.
Does mist between the panes explain mould on the sill?
Record both observations and have them assessed. They concern different places; one does not prove the cause of the other.
Should I replace the window straight away?
Establish why the area is wet first. An assessment should guide any decision about repair or replacement.
Found visible mould? Read the cleaning precautions and when to seek help.
