WASHINGTON, DC—The proposed addition to the Carnegie Library in Mount Vernon Square that would house the new home of the International Spy Museum could be delayed due to design concerns raised by the D.C. Historic Preservation Office.

The project “continues to raise a number of substantial preservation concerns that warrant further study,” according to staff of the Historic Preservation Office. Those concerns were detailed in a report given to the Historic Preservation Review Board before is session last Thursday, according to the Washington Business Journal.

The renovation would add 65,000 square feet, doubling the library's usable space, with two new pavilions and a build-out of below-grade space. Staff of the Historic Preservation Office say the design as is would reduce open space in Mount Vernon Square and obstruct the view of the original library building. In its report, staff recommended changes in the design to improve views from the southeastern and southwestern sides of the building.