Damp in an apartment: causes, prevention and treatment
Stains, mould, smells: damp damages a home and your health. How to find its cause and treat it for good.
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Damp is one of the most common defects in homes, especially in coastal cities and in wet rooms. It causes stains, mould, blistering paint and smells, and can affect health. Treating it for good means finding the cause. It is also a key point in the viewing checklist.
The four main causes
| Cause | Signs | Solution |
|---|---|---|
| Condensation | Misting, mould in corners, bathroom | Ventilate, air, gentle heating, extractor fan |
| Infiltration | Stains after rain, under a terrace or on the facade | Redo waterproofing, seals, windows |
| Rising damp | Damp at the base of ground-floor walls | Specific wall treatment |
| Leak | A localised stain that spreads, unusual water bill | Find and repair the leak |
Everyday prevention
- Air the home every day, even in winter.
- Use the cooker hood when cooking and the bathroom extractor.
- Avoid drying laundry indoors without ventilation.
- Leave a gap between furniture and outside walls.
- Keep an eye on shower and bath seals.
Treating it for good
Cleaning mould and repainting is not enough: you must first remove the cause. For infiltration from a terrace or the facade, the managing agent must act on the common parts. For a leak at a neighbour’s, warn them and, if needed, the insurer; see landlord insurance.
Case study
In a seaside apartment, mould returns every winter in one bedroom. A professional identifies condensation, made worse by a very airtight window and no ventilation. Fitting an air vent and an extractor in the adjoining bathroom, combined with daily airing, solves the problem without major works.
Before buying
- Look at corners, ceilings, the base of walls, cupboards
- Be wary of very fresh paint on a single wall
- Ask the managing agent about known leaks
- Visit after a rainy spell if possible
By the sea, see also buying by the sea. Hidden damp may count as a hidden defect.
Key points
- Find the cause before treating.
- Condensation is fought with ventilation.
- Infiltration from common parts is the managing agent’s job.
- Check for damp before buying.
Common mistakes
- Repainting without treating the cause.
- Blocking air vents to avoid draughts.
- Drying laundry in a closed room.
- Leaving a small leak unattended.
For regular upkeep, see the maintenance calendar; for summer comfort, keeping a home cool.
Damp by the sea
In coastal cities the air is humid all year. Daily airing, extractors in the bathroom and kitchen and moisture-resistant materials become essential.
FAQ
Is a dehumidifier enough?
It helps with condensation, but does not solve infiltration or a leak.
Who pays if the damp comes from a shared terrace?
Works on common parts fall to the owners’ association; report the problem to the managing agent.
Is damp a reason to negotiate when buying?
Yes: get the treatment priced and factor it into your offer.
Is anti-damp paint enough?
It limits mould but does not solve infiltration or a leak: treat the cause first.
Can damp come from the neighbouring apartment?
Yes, a leak at a neighbour’s or in a shared pipe can cause damage; tell them and the managing agent quickly.
Does damp affect health?
Mould can irritate the airways, especially for children and people with allergies; treat it promptly.
Official sources
The rules and amounts quoted come from these official texts and websites. They change with finance laws: check the version in force before deciding.
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