In the chambers of Durham's City Council and County Board of Commissioners, historic preservation has run up against hard times.

In particular, both bodies have wondered whether the property-tax break for "historic landmarks" is worth the loss to the public's coffers.

"This is having a big impact on our tax values," county Commissioner Becky Heron said this week.

Durham city and county take part in a state program, under which designated historic properties are taxed at 50 percent of their assessed value. For example, according to the city/county planning department, designation for the 15 properties gaining "landmark" status in 2008 took more than $11 million off the city's taxable rolls - or about $62,000 per year at the current tax rate of 54 cents per $100 valuation.

Six properties are up for City Council approval Monday night.

"As supportive as I have been of this program, I keep coming back to a question that I struggle with," Councilman Mike Woodard said. "The historic value versus the economic value of these properties."

According to Preservation Durham, any property more than 50 years old with its "architectural integrity" maintained may be considered for "historic" designation. In the past two weeks, commissioners and council members have approved stricter criteria for "historic landmarks," and suggested an annual cap on designations, cutting the 50 percent deduction and otherwise modifying the program.

"Is it really the city's intention to provide 50 percent tax credits for the entire population of historic homes?" Councilwoman Diane Catotti said.

Steve Cruse, former historic-property specialist with the planning department, said in 2007 there were 3,761 sites and places of some "historic" nature in Durham County, more than 2,000 of which had some kind of official recognition as such. "Seventy-some" properties have "landmark" qualification for the 50 percent tax break, Planning Director Steve Medlin said this week.

Medlin did not have a figure yet for the total "landmarks" revenue loss. That's one thing the planning department is looking at, along with the options legally available to the city and county under the state's rules. Commissioner Ellen Reckhow and Councilman Eugene Brown - who sells older houses for a living - have said the preservation incentive may have served its purpose. But Gary Kueber, who writes the "Endangered Durham" blog on local history, has the opposite opinion.

Properties that meet the "landmark" criteria "are essential pieces of the historic fabric of Durham," he said.

Kueber said he was speaking from a preservationist point of view, and not as an employee of Scientific Properties, which owns one of the buildings up for "landmark" approval Monday.