Damp in the walls. Mould behind the furniture. Dry rot revealing itself as soon as you remove the skirting boards. These are the classic issues in hidden defects cases involving real estate. The case law on these problems is extensive and offers important guidance — both for the buyer who wishes to assert his rights and for the seller defending himself. This article sets out the practice.
The threshold: not every damp problem qualifies
First an important nuance. Damp is commonplace. Many homes deal with it to a greater or lesser extent — through condensation, rising damp, leaks or ventilation issues. Not every damp problem is automatically a hidden defect in the legal sense.
The Liège Court of Appeal has summarised this nuance succinctly: since any normally attentive and informed person can appreciate that a bathroom in a cellar without natural ventilation will cause damp problems, the presence of damp in that location cannot constitute a hidden defect (Liège, 11 February 2013, JLMB 2013, 2093).
In other words: damp that you should reasonably have known would arise is not a hidden defect. It is your own lack of care to buy such a space without hesitation. A cellar, an extension without insulation, a bathroom without a fan — for these spaces a heightened alertness applies to the buyer.
The positive side: structural damp is a hidden defect
Where the damp problem does not arise from a logically foreseeable structural weakness, but from an actual defect in the property, the matter is different. Examples from case law:
Serious damp affecting the occupants' health. In the case dealt with by the Liège Court of Appeal in 2013, the problem was so serious that the buyers were forced to rent another home temporarily. The court awarded them damages for the "loss of enjoyment" linked to the double rent. Here the damp was clearly more than an inconvenience — it made the property effectively unusable.
Damp affecting the building structure. When damp penetrates wooden beams, foundations or load-bearing masonry, thereby affecting the "health of the construction", it qualifies as a hidden defect without discussion (Mons, 9 September 2013, JLMB 2015, 317).
Damp caused by hidden construction defects. A cellar not built as a waterproof tank although technically necessary, an incorrectly placed damp-proof course, missing drainage — these are structural defects not visible to a normal buyer.
Proof of damp at the time of purchase
A central legal condition: the damp problem must have existed at the moment of purchase. A damp problem that only arises three years after the purchase and whose cause does not date back to before the purchase is not a hidden defect.
But case law applies a flexible rule: it is sufficient that the problem was "at least in seed" present at the time of purchase (Cass., 27 April 2020, AR C.19.0337.N). An insufficiently waterproof cellar will sooner or later lead to damp infiltration — even if the problem only manifests when the groundwater level rises or when the previous owner is no longer maintaining it.
What must you therefore show? Not that the damp was visible at the time of purchase, but that the cause of the damp — for example the defective waterproofing, the incorrectly placed damp-proof course — already existed. In practice, a court-appointed expert provides this proof.
Dry rot: a special case
Dry rot (Serpula lacrymans, also known as "house fungus") is a fungal growth that attacks wooden construction elements. A true nightmare for anyone who discovers it after purchase, since remediation often costs tens of thousands of euros and requires extensive works.
What is special about dry rot: it often develops slowly and only becomes visible during major works — sometimes years after the purchase. The Antwerp court dealt with a typical case: a buyer discovered dry rot only seven years after purchase, during renovation works. He issued proceedings immediately. The court held that the short time limit had not been exceeded, because the defect was only discovered at that moment and no intermediate works had made proof impossible (Antwerp Court, 16 February 2016).
In the same case two further elements played a role. The seller, who had only owned the property for two years and then sold it to the claimant buyer, could rely on the exoneration clause because he had no knowledge of the problem. But the original property developer and the architect remained liable through the qualitative liability claim — an important strategic element for the buyer in the case of a property still within the ten-year liability period.
The specialised seller and the presumption of knowledge
When you buy a home from a contractor, a construction professional or someone who has worked on the property for years, the burden of proof shifts in your favour. The Liège Court of Appeal expressly held that a professional seller who was aware of damp problems and nevertheless sold the property "as a normal item" does not act in good faith and cannot rely on the exoneration clause (Liège, 23 July 2021, TBBR 2022, issue 4, 227).
The same logic applies to the self-builder. The Court of Cassation confirmed in 2019 that a self-builder too "must know" that appropriate measures are required to, for example, make a cellar watertight. Anyone who deviates from those standards without a professional can no longer use his ignorance as a shield (Cass., 18 February 2019, AR C.18.0346.N).
In practice: check the seller's capacity, request the PID (Post-Intervention File), check whether there are traces of works carried out by the seller himself. When you can show that the seller was actively involved in the construction or renovation, you have a strong position.
Camouflage and bad faith
A third category of cases: the seller who has actively camouflaged the problem. Stud walls in front of damp walls, paintwork over mould, tiled floors over cracked cellar floors. As soon as you can show that the seller deliberately carried out works to hide the problem, the exoneration clause falls away. Moreover, this opens the way to fraud (Article 1116 old Civil Code).
Proof of camouflage often comes to light during renovation works. When during works you discover that a wall has been recently placed — for example through a date stamp on plasterboard — or that there is fresh paintwork on a wall hiding fundamental damp problems, document this carefully. Photos, possibly a bailiff's report of findings, can be decisive afterwards.
Practical tips for the buyer
Document immediately. As soon as you discover damp, mould or dry rot: photos, videos, dating. Do not try to repair the problem yourself before an expert has been able to establish it — otherwise you lose the evidential value.
Engage an independent technician quickly. An initial assessment by a damp control firm or building expert is useful to establish the seriousness and the cause. It is no substitute for a court-appointed expert, but it does build pressure for negotiation.
Formally serve notice on the seller. A registered letter with a detailed description and photographic material is a minimum necessity. This preserves your rights within the short time limit.
Request a court-appointed expert if necessary. When amicable negotiations stall, a judicial expert investigation is often indispensable. Do not wait too long: combine the request with a substantive claim, so as not to allow the short time limit to expire.
Practical tips for the seller
Be transparent about what you know. When you have suspicions of damp, mould or dry rot, mention them in the compromise. A specific risk acceptance by the buyer is your best defence.
Do not carry out superficial cosmetic interventions before the sale. Painting over mould, tiling over cracked floors, placing stud walls — these actions are risky. As soon as they are interpreted as camouflage, your legal position falls away.
Keep documentation of previous works. When you have addressed damp problems in the past through a professional, keep the invoices and certificates. They show that you acted carefully and that you were not trying to hide the problem.
For the full legal framework on hidden defects in real estate, consult our pillar article.
Have you discovered damp, mould or dry rot after purchase, or are you being pursued yourself? A quick legal analysis can make the difference between a successful claim and a late file. Contact us at info@reius.be.