Droplets on windows or a damp corner do not tell you where the moisture comes from. Note when the problem occurs and act in time. With recurring problems, a possible defect in the building must also be checked.
Ventilate and monitor humidity
Ventilate regularly and remove humid air after cooking and showering. Do not block ventilation openings, and use and maintain devices according to the manufacturer's instructions. If you dry laundry indoors, make sure the extra moisture is removed.
Use a simple meter to monitor temperature and relative humidity. The National Institute of Public Health (NIJZ) recommends relative humidity between 40 and 60 percent. Record several measurements at different times of day; a single measurement does not explain the cause.
Condensation or a leak?
With condensation, water vapour in the air turns to liquid on a colder surface. Droplets on cold glass and problems after cooking or showering may be related to condensation. Stains that appear or grow after rain or when pipes are in use may indicate a leak.
These are signs for further checking, not a final diagnosis. Causes can overlap; without an inspection the cause or responsibility cannot be reliably determined.
Don't just paint over mould
The source of moisture must be removed first. Adapt cleaning and repair to the extent of the problem and the material, and follow the instructions of a qualified contractor or the manufacturer of the product used. If the problem recurs, an inspection is needed.
What to send the building manager?
- The building address, entrance and flat number.
- A photo of the whole surface and a close-up of the stain.
- The date you noticed it and whether it is linked to rain, cooking or showering.
- Any measurements and measures already taken.
- A contact for arranging an inspection.
Report the problem through the Practic portal (opens in a new window). If water is actively leaking, also use the emergency contact published for your building.
Official source
NIJZ: Preventing mould indoors (in Slovenian) (opens in a new window).