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A couple who claimed emissions from a nearby whisky warehouse left their home coated in black staining lost a landmark Court of Session battle against Diageo Scotland Ltd, even though a judge accepted that ethanol released during whisky maturation caused "whisky fungus" to grow on their property.
In a case that began in 2014, scientists were called to the stand to give evidence on the effects of Baudoinia, a fungus commonly known as whisky fungus, which caused black staining on their home.
Thomas Chalmers and Gail Chalmers, who live about 350 metres from Diageo's bonded warehouses in Bonnybridge. The couple purchased their house in the modern estate of 200 homes at Woodlea Gardens in 2002.
Diageo has operated a bonded warehouse complex southwest of the house, beyond a nature reserve, since the 1980s, with nine bonded warehouses for maturing whisky on site.
The case argued that ethanol vapour escaping from the site promoted Baudoinia growth on their property, which required cleaning and was “unsightly and depressing”.
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The couple sought around £40,000 in damages for the cleaning and nuisance caused by the fungus, and also claimed the staining reduced the value of their property and their enjoyment of their home.
In a ruling issued as 2026 CSOH 104, Lord Young dismissed the action and ruled in Diageo's favour, ending the dispute.
However, because it is believed to be one of the first of its kind, the judgment includes findings that Scotland's whisky industry and communities living near maturation warehouses are likely to scrutinise closely.
Lord Young accepted that ethanol emissions from Diageo's warehouses caused whisky fungus to grow on the property, but held that the couple failed to prove the fungus caused the wider blackening they complained of and, in any event, that the effects would not have amounted to an actionable nuisance.
In the opinion, Lord Young found: "Baudoinia fungus has grown on the pursuers' property because of ethanol vapour released from the defenders' bonded warehouse."
Lord Young noted that cleaning the affected surfaces cost around £500 a year.
A central part of their case was that Baudoinia acted as a "first coloniser", encouraging other organisms and deposits which eventually caused the black staining visible on buildings and outdoor surfaces. The court found the scientific evidence supporting that theory insufficient.
Lord Young said that, had nuisance been established, he would have been prepared to find Diageo liable. He criticised the company's response to concerns and described its attitude toward the issue as "distinctly uncurious".
The Court of Session accepted the scientific link between ethanol emissions and Baudoinia growth, yet held that proving that link alone is not enough to establish a legal nuisance.
Lord Young said that, had nuisance been established, he would have been prepared to find fault with the company, noting its internal awareness of the issue and describing its attitude to residents' concerns as "distinctly uncurious".
He finalised by granting a decree of absolvitor in favour of Diageo, finding that the couple ultimately had not proved the fungus substantially caused the blackening they complained of; and that even if it had, the effects would not have amounted to an actionable nuisance.
Lord Young said: "I accept that there is a degree of interference with their use and enjoyment of their property.
"But I am not persuaded that the pursuers have proved that it is of such a degree that it goes beyond what a householder in an urban development close to an established industrial estate can be expected to tolerate."
Adding that, "I shall reserve all issues of expenses meantime."
A Diageo spokesperson said: “We welcome the decision by the Court of Session to dismiss this case.
"The Court’s decision confirms that there is no credible scientific evidence that temporary discolouration is caused by any single environmental factor, including ethanol.”