Dry Rot or la Mérule

[yann]

Prospective buyers interested in property north of the Loire might like to know that there is official recognition of a growing incidence of dry rot or, to give its French name, la Mérule, especially near coasts. The department of La Manche has even issued documents emphasising the need for vigilance. Contact me if you would like more details.[6]

[ross.e]

It seems mérule is not always mérule.....

 

In our compromise de vente there is a clause concerning mérule...if found we get out of jail free.

The situation now is that the diagnostic has found other species of dry rot namely -

Donkioporia and Coniophore.

 

I can also find many examples on the internet that state the following or similar -

 

"Le Coniophore est également un champignon de pourriture cubique. Le nom scientifique est Coniophora puteana."

 Is mérule a description of the mérule species only or is it used as a general term to cover -

'mérule et autres champignon lignivore' as is so often stated in .gouv.fr websites.

Is there any precedent here....??

 

[ventodue]

Ok, a certain amount of caution needs to be exercised here.

1.  Both Coniophora puteana and Donkioporia expansa are what are commonly called 'wet rots' in English.  As this name suggests, their presence indicates that there is a significant mount of water in or on a structure; and while, it may generally be considered to be Not Good, it is not unusual or worrying to have one or other (even both ...!) growing over the walls of a damp* cellar, for example.

In  most circumstances, it's not something to be too concerned about.  Because it needs a generous and constant supply of water, the fungus won't suddenly start climbing up through the house.  That said, if it does get into say, the sodden timbers of an exposed roof, its ravages can be spectacular.  But make the roof water-tight, and the fungus will disappear.

* Damp as in more than 40%, or 'running wet'.

2.  'Dry rot' or mérule are layman's terms used to describe a number of different, and much more abundant, species of 'dead wood consuming' fungi.  This reflects the information given in the gouv.fr websites that you've found.

The most notable of these dry rots is Serpula lacrymans. The problem here is Serpula lacrymans in particular has the ability to transport its own water with it as it grows, thereby enabling it to expand over dry areas and reach timber which wouldn't otherwise be acessible to it.  So this is the one to be most concerned about in terms of potential structural damage.  It's also the one to be most concerned about in terms of potential health issues (some people can react to breathing in the spores).

There's much more to be said on the subject, mainly based around, "Don't Panic!  They're only trying to get some money out of you!", but I'll stop there for now.

HTH

Craig