The Hampton-Preston Mansion, one of the city's oldest homes and a favorite landmark, has a leaky roof and serious damage to the front porch.
The problems are so worrisome, the Historic Columbia Foundation no longer allows tour groups to gather at the front door.
It closed a second-floor balcony used for special events and even moved candlelight tours this Christmas to another site partly out of sensitivity to the issue, director Robin Waites said.
Structural problems at the historic gem, toured by thousands of visitors each year, are being fixed. But they highlight a dilemma for local government leaders.
Since accepting ownership of five historic properties in 2006, Columbia and Richland County have not assessed their condition to determine what structural problems exist and how much it would cost to fix them.
Councilman Greg Pearce, Richland County Council's liaison to the Historic Columbia Foundation, said it's time to move beyond well-intentioned repairs at the houses to professional fixes.
"Nobody has ever gone in there ... and looked at the houses and said, 'If you want to preserve these in perpetuity, this is what you do,'" he said.
The structures previously were owned and maintained by a special purpose district.
The process of assessing the needs of the homes has begun and the figures could be staggering.
Three years ago, the county devoted $1.16 million to restoring the Woodrow Wilson Family Home.
Once an architectural firm that specializes in caring for historic buildings examined the property, estimates doubled to $3.4 million. Now the home - closed to the public in October 2005 - is stabilized but unfinished.
Waites said she didn't know when the work would be done and the home reopened to visitors.
Meanwhile, spring rains revealed problems with the roof of the Hampton-Preston Mansion. Richland County Council shelled out $100,000 to replace the roof.
Last month, the council agreed to shift $340,000 from the Wilson project to the Hampton-Preston Mansion so a thorough assessment could be done and the porch fixed, too.
The mansion will stay open to tours during repairs, which should be completed by next fall, Waites said.
Shifting the money was not ideal, but "it's the best use of the dollars for the needs we have," she said.
The county owns the Hampton-Preston Mansion and the Woodrow Wilson Family Home.
The city owns the Robert Mills House, the Mann-Simons Cottage and the Modjeska Montieth Simkins House.
The Historic Columbia Foundation is caretaker of the five historic structures, which it manages as house museums.
Money to support Historic Columbia comes from the county's 1 percent tax on restaurant meals, money dedicated to catering to tourists.
Richland Councilman Damon Jeter said it's important to find out how much it would cost - and how long it would take - to bring the two historic house museums "up to par."
"It's going to take several million dollars in phases," he said. "We'd probably have to spread it out over several years."
In the past, Waites said, some quick fixes at the Hampton-Preston Mansion on Blanding Street led to bigger problems.
Patching seams on the metal roof 10 years ago caused the leaks that are occurring now. And without peeling back the roof, she said, it's impossible to know how bad the structural problems are at the point where the porch connects to the house.
But other problems are visible to the eye: cracks in the foundation and in the front steps, old termite damage in the joists supporting the porch.
Waites, director of Historic Columbia since 2004, said the porch's flooring system needs to be addressed right away.
The county's recent allocation will pay for a $65,000 assessment of the building's other needs by the architectural firm John Milner Associates of Louisville, Ky.
The Woodrow Wilson house "definitely was in worse shape" than the other properties, Waites said. "It wasn't safe for visitors when we closed it. Hampton-Preston is not in that kind of condition."
Historic Columbia owns two buildings, bringing to seven the number of structures for which it is caretaker. The oldest of the bunch, the Seibels House and Garden, where its offices are located, dates to 1796.
But it's the nearby Hampton-Preston Mansion that holds a special place among visitors.
"It's really the most complete story that we have to offer," Waites said.
"The family that lived in that house from 1823 to the 1860s is a story that's well documented, and we also have quite a large number of collections from the family."