The Ouray City Council on Tuesday signed off on a plan to expand the historic Columbus Building, with a series of changes the owner says is necessary to cover soaring restoration costs.

Councilors unanimously agreed to amend the planned unit development for the property at 740 Main St. to allow a three-story, 600-square-foot addition to the rear of the building and a larger rooftop seating area.

Building owner Stuart Gillespie has embarked on a comprehensive renovation of the building at the south...