Already surrounded by scaffolding is the house that architect Frank Lloyd Wright designed for Edgard J. Kaufmann as a weekend retreat in the 1990s, built on a vast tract of land in the mountains of southwestern Pennsylvania, literally over a small waterfall formed by the Bear Run stream. It is one of the most famous buildings of the 20th century, a veritable manifesto of organicist architecture.

But now it is starting to leak: almost 90 years after it was built, there is an urgent need to deal with more than 60 water infiltrations that are threatening the integrity of the building: rain and melted snow have penetrated the roof and damaged the interior of the house.

The team is pumping liquid mortar into the hollow walls, which the architect had filled with sandstone that had deteriorated over time, to prevent water from collecting inside, and installing lead seals where the walls meet the roofs or terraces.

Overseeing the work is Justin Gunther, director of the Fallingwater House, who told the Wall Street Journal that the building's condition was due to the inherent complexity of certain design choices, rather than a lack of attention on the part of the architect: 'Wright went beyond traditional building patterns to achieve something extraordinary and used the most advanced technology available to him.

7 million US dollars is the estimated cost of the work, a remarkable figure given that Wright needed 'only' $148,000 to build the house (about $3.2 million in today's currency). Visits to the site, which has been open to the public for years, will continue throughout the construction period and even include a tour of the house from the scaffolding.