The New Barn at Harmondsworth, built around 1426, is considered a remarkable example of medieval architecture and is the largest surviving timber-framed barn in England. But according to conservationists, the vibrations from thousands of additional aircraft movements under the third runway scheme could cause irreversible damage to the ancient structure.

The Guardian reported exclusively on the threat, citing campaigners who say the barn could be 'shaken to pieces' by the constant low-frequency vibrations from planes flying overhead. The barn, located near the airport's northern boundary, would sit directly under the flight path of the proposed new runway.

Heathrow Airport has long argued that expansion is essential for UK economic growth, creating jobs and increasing capacity. The third runway project, which has been debated for decades, received government approval in principle but faces ongoing legal and environmental challenges. The airport has said it will mitigate noise and vibration impacts through modern aircraft technology and operational measures.

However, heritage groups remain unconvinced. The New Barn, with its massive oak frame and thatched roof, has survived for six centuries — including two world wars and the original construction of Heathrow in the 1940s. But the scale of the proposed expansion, which would add an estimated 260,000 flights per year, is unprecedented.

Historic England, the public body that advises on heritage, has not yet issued a formal position on the specific threat to the barn, but it has previously raised concerns about the cumulative impact of airport expansion on the historic environment. The barn is a Grade I listed building, the highest category of protection, meaning any development that could damage it must be considered with extreme care.

The public consultation on the airport's expansion plans closes on 1 September, giving local residents, heritage groups, and other stakeholders a final opportunity to voice objections. Campaigners are urging people to write to the government and the airport to demand that the barn be protected.

Heathrow has stated that it will conduct a full environmental impact assessment, including vibration modelling, before any construction begins. But critics argue that the damage may be unavoidable once thousands of planes are flying low over the site every day.