The inclusion of Fallingwater on the United Nations’ World Heritage List of significant cultural landmarks remains a bit of a cliffhanger.

The U.N.’s World Heritage Committee decided in a close vote Sunday to refer the United States’ submission of the iconic Frank Lloyd Wright-designed home in Somerset County’s Laurel Highlands and nine of his other buildings in seven states for future consideration, according to the Western Pennsylvania Conservancy, which owns Fallingwater and worked on the designation.

Lynda Waggoner, Fallingwater’s director, attended the committee meeting in Istanbul, Turkey, and said that although the committee agrees Wright’s architecture is globally important, it is requiring additional documentation.

“While we would have preferred the series be inscribed at this session, we feel the decision to refer is fair,” Ms. Waggoner said in a release posted on the conservancy’s website. ”A serial nomination like ours is a very complex undertaking and it is certainly not unusual for such nominations to be reworked multiple times before inscription is achieved. We appreciate the opportunity to address the committee’s concerns in the coming months and hope for inscription of the series in a few years.”

The 10 Wright buildings, formally nominated by the U.S. Department of the Interior in January 2015, would have been the first American modern architecture on the World Heritage List, which includes such cultural sites as the Sydney Opera House in Australia, the city of Brasilia in Brazil, and various buildings designed by Antoni Gaudi in Barcelona, Spain.

The World Heritage site listing was initiated in 1972 under an international treaty for natural site conservation and cultural site preservation. The list now includes more than 1,000 sites in 161 countries, including Stonehenge in England, the Taj Mahal in India, the Great Barrier Reef in Australia, and, in the U.S., Yellowstone National Park, the Statue of Liberty and Independence Hall, the only listing in Pennsylvania.

Fallingwater, which overhangs a waterfall on Bear Run, was built by Wright in 1936 as a summer retreat for Pittsburgh department store owner Edgar Kaufmann Sr. The conservancy was given the property by Edgar Kaufmann Jr. in 1963 and operates it as a museum that attracts more than 160,000 visitors annually.

A reworked Wright nomination can be resubmitted by Feb. 1 for consideration during the next heritage committee session, with a decision by the summer of 2018.

Don Hopey: dhopey@post-gazette.com, 412-263-1983, or on Twitter @donhopey

First Published: July 23, 2016, 4:00 a.m.