If the windows are wet again this morning, start with a dry cloth. Where the moisture sits matters more than how much of it there is. Droplets you can wipe from indoors usually point to condensation. Mist inside a sealed unit or water appearing around the frame after rain calls for a different check.
| What you see | First check |
|---|---|
| Room-side droplets | Wipe the inside dry. Check whether the water returns after sleep, cooking or showering, and whether vents and extractors are working. |
| Mist between panes | If both safely accessible faces are dry and the mist stays, photograph it and check the sealed unit’s warranty. |
| Outside moisture that clears | Watch whether it disappears as the morning warms. |
| Wet frame or plaster after rain | Note where water first appears and check the sill, gutter and perimeter from ground level. |
If the water wipes off the room side
Warm, moist indoor air can leave droplets when it reaches cold glass. A bedroom can be affected overnight, and a kitchen or bathroom may mist up after cooking or showering. Wipe the glass and sill dry, then look for the routine that brings the water back.
- Keep trickle vents open where fitted. Check that curtains or blinds aren’t covering the vents.
- Run the bathroom or kitchen extractor during showering or cooking and afterwards as needed. If a cooker hood only recirculates air, use another means of ventilation to remove moisture.
- Keep steam from spreading by closing the kitchen or bathroom door while those rooms are in use. If washing has to dry indoors, use a ventilated room and keep the moisture from spreading through the rest of the home.
See Energy Saving Trust’s advice on window ventilation and condensation.
If the mist stays between the panes
If the glass looks cloudy after you’ve wiped the inside, check the outside only if you can reach it safely. Mist trapped between the panes of a sealed double-glazed unit can indicate a failed seal. Take a photo, check the warranty and ask a glazier if the sealed unit can be replaced in the existing frame. Exterior condensation on an otherwise sound window can clear as the morning warms.
If the frame or plaster gets wet during rain
Dry the area and note where the water first reappears. A wet lower corner after wind-driven rain, or a stain spreading on the plaster above the window, is worth investigating as possible water ingress. From ground level, look for gutter overflow, damaged perimeter seals or water pooling on the sill. Keep any designed drainage openings clear. If you can’t trace the route of the water, get the window and surrounding wall checked before resealing anything. The guide to identifying damp covers signs elsewhere in the room.
Keep a three-morning record
- On the first morning, photograph the window and record which surface is wet, which rooms are affected and whether it rained overnight.
- Try the ventilation changes above and note when you cooked, showered or dried washing indoors.
- On the next two mornings, check the same windows before wiping them. Note whether the droplets are less widespread and whether any stains or mist remain.
If damp patches or mould keep returning, ask for the underlying cause to be investigated. If you rent, report it to your landlord or agent with dated photos and notes on when it occurs.
