Parts of Frank Lloyd Wright's 1924 EnnisBrown House in Los Angeles were labelled unsafe for habitation by the city's authorities last week following a hill collapse close by.
Bob Steinbach, a spokesman for the city's department of building and safety, warned of the need to urgently address some of the building's structural problems after conducting an inspection of it in the wake of Californian mudslides.
After an initial inspection last week, Steinbach put the cost of damage at around $500,000 (£260,000) but now believes it could be as much as $1 million (£522,000).
At present, the rear wall of the building's parking deck and its chauffeur's quarters are classified as being in need of urgent attention, and may not be occupied after being weakened by the weather.
Steinbach said: 'The building was built in the 1920s with concrete blocks, which were not reinforced in any way, prior to the design codes we now use.' The official noted that the main part of the house fared much better in the rains because of a recent programme of structural reinforcement.
South California has seen a series of heavy rainstorms this winter that have caused mudslides close to the Wright-designed landmark, which has been used in a number of Hollywood films, including Blade Runner.
The bad weather has catalysed plans by the building's owner, The Trust for Preservation of Cultural Heritage, a private non-profit organisation, to address the building's structural problems. It has been considering different design options for the last two years.
The Ennis-Brown House has been designated as a city, state and national landmark in the United States. It is on the World Monument Fund's Most Endangered Site list, along with the Great Wall of China and the Quetzalcoatl Temple in Mexico.