Moisture (fugt) is water where it shouldn’t be — inside walls, under floors, in ceiling structures or behind tiles. It is one of the most common and costly building defects in Denmark. Moisture causes rot, mould and material degradation.
Why does it matter to you?
Mould can affect indoor air quality and cause health problems. Moisture damage can render a building uninhabitable. And repair is expensive — typically DKK 50,000–500,000+ depending on extent.
Catching and dealing with moisture early is far cheaper than waiting. If you know the signs, you can act before the damage grows.
What causes moisture damage?
Construction moisture: New buildings contain large amounts of moisture from concrete and mortar that needs to dry out — typically over 1–2 years.
Condensation: Warm, humid indoor air condenses on cold surfaces (windows, cold walls). Addressed through better insulation and ventilation.
Rising damp: Older houses without a damp-proof course can absorb water from the ground through capillary action. Typically visible as flaking and salt efflorescence in the base wall.
Water ingress: Leaky roofs, windows, walls and foundations let rainwater in.
Installation leaks: Burst water supply pipes, drains or heating systems.
Signs of moisture
- Staining or patches on walls and ceilings
- Peeling paint or wallpaper
- Mould growth (black, green or white patches)
- Musty or earthy smell
- Condensation on the inside of windows
Frequently asked questions
What is the legal indoor humidity limit?
There’s no fixed legal limit for relative humidity, but the Danish Health Authority recommends 40–60% relative humidity indoors. Above 70% creates risk of mould growth.
Can I just paint over mould?
No. Mould must be properly treated — typically by mechanical removal followed by cleaning with a disinfectant. Painting over mould hides the problem temporarily but doesn’t solve it.
When should I call an expert?
If you see mould on more than 0.5 m², if the smell is strong, or if you can’t identify the source — contact a building surveyor or mould specialist.
Does my insurance cover moisture damage?
Sudden water damage (e.g. a burst pipe) is typically covered by home insurance. Moisture that has developed gradually over time is typically not covered.