Mushroom contamination makes French couple’s home a ‘health risk’

A couple in southern France have described how a mushroom contamination has spread throughout their house, forcing them to seek legal advice and may even require them to knock down and rebuild their home.

The house is located in Saint-Jean-de-Verges, Ariège (Occitanie). The mushroom in question is the merula, a wood-eating fungus (scientific name Serpula lacrymans), also known as 'dry rot'.

The fungus grows on wood, often as a result of damp or poorly ventilated conditions in buildings. It can also spread from wood to masonry walls, and is relatively common in cellars. It is also known as “dry rot”, because it can spread unseen behind wooden beams and walls, and is only discovered when wood starts to disintegrate.

“It started with a big white mushroom that we discovered in a corner, behind the sofa,” the homeowners recounted to local newspaper La Dépêche. They scraped it away and did not think much more of it. But later, when they returned to the house the same day, they realised that it “smelled like a forest, like when you go to pick mushrooms”.

The problem continued to spread, and the couple has now launched a legal case and taken advice to investigate whether their house has construction flaws that led to the contamination. They have also called in specialist fungus removal experts.

However, they believe they may be forced to knock down part of the house structure and redo it, in order to get rid of the problem completely, due to the spread of invisible spores. 

They have launched an online crowdfunding campaign to raise funds for the project, and fear that the cost of the work could amount to €50,000, on top of fees and costs already accrued for legal advice and inspections. They also fear that their house is becoming “increasingly unhealthy” and that “our health and that of our daughter is at risk”.

It comes after another couple, this time in Pas-de-Calais, reported the same issue to TF1 in January. They said they had bought a house, but just a month after they moved in, the woodwork started to crumble. An inspection identified the cause as dry rot. The couple are now looking to cancel the sale, and claim they were not told about the rot beforehand.

The merula mushroom (mérule in French) is often found in Brittany and Nord-Pas-de-Calais, but can be found anywhere in France.

How to check for dry rot (mérule)

It is advised that people buying a house in France have a mérule inspection by a qualified and COFRAC-certified diagnostic technician, particularly in high-risk areas. These can be found through a notaire or professional housing associations. It is not mandatory when purchasing a property, but is recommended.

Even if you already own your home, an inspection is recommended to be done every six months, and costs between €200 and €400.

This diagnostic is usually provided by the same experts who cover other wood infestations, such as termites.

Once the fungus has infiltrated your home, it can be difficult to get rid of without the help of a professional. If your home is less than 10 years old, you should be covered by assurance décennale insurance in the case of an infestation.

For older properties, you can negotiate with your insurer to get additional cover against mérule damage

This is a map of higher-risk departments with more information on the details and cost of inspections.