One of the biggest and priciest mansions in Santa Fe was finished last September, but nearly a year later, the home still doesn't show up on county tax rolls.

The 23,105-square-foot residence perched on a ridge above northeast Santa Fe is so unlike other homes in the city that there is nothing comparable to use as a guide in assessing its value, a county official said last week.

Santa Fe County Assessor Domingo Martinez said his staff has spent the better part of the last year trying to get information about what it cost owners Andrew and Sydney Davis to build the home in order to determine its value for tax purposes.

Getting that information, Martinez said, hasn't been easy.

Martinez said his appraisers first tried to inspect the house — a showcase of fine stonework and glass with landscaped yards on a hilltop overlooking Hyde Park Road — last October.

After twice being turned away by workers, Martinez said, his staff did get permission to enter the building. But after looking at the house — which boasts a cavernous multicar garage — appraisers decided it would be difficult to gauge the value of the one-of-a-kind property. Martinez said homes normally are appraised based on square footage and the selling prices of comparable homes, but when there is nothing similar, a cost-based approach is used to determine the value.

"That's when we started asking for what their costs were to build the actual house or all the improvements," Martinez said. "We had to beg, borrow and plead with them to give us the information."

For example, the assessor said, floor plans for the house requested last October or November weren't produced until April or May.

The New Mexican reported in 2005 that the Davises declared on documents filed with the Santa Fe Planning and Land Use Department that the house and a 3,058-square-foot guesthouse would cost about $4.5 million to build. The same story quoted a Santa Fe builder who estimated the project could cost about $10.5 million.

Martinez said the county has paid a contract attorney about $800 to negotiate with Davis attorneys on the case. At one point, Martinez said, he considered trying to subpoena information but reconsidered after information began to flow more quickly.

But attorney Frank Herdman said his clients have provided all the information requested by the Assessor's Office in a timely fashion even though the level of detail being requested regarding the construction costs "far exceeds anything that is typically asked of a taxpayer."

"The assessor has all of the information to establish the value for the house," Herdman said. "We have no control over when they complete that process."

Herdman said the Davises "provided more than 30 pounds of documentation of information regarding the house," in seven separate requests from the assessor. "We met on three occasions with employees of the Assessor's Office."

Herdman said the Assessor's Office has also asked that the Davises commission their own appraisal and provide a copy of it and that the county's own appraisal process will be on hold until that is done.

Martinez said he hasn't sat in on every meeting regarding the matter but was under the impression that the Davises already had intended to get their own appraisal and that the county has simply requested a copy.

If the valuation hasn't been completed yet, Herdman said, it's not because of lack of cooperation on the part of the Davises.

"It's my impression that the Assessor's Office is overwhelmed with property tax protests," Herdman said. "That may very well explain why they have yet to get around to assigning a value to the house as of this date."

"That's besides the point," Martinez said. "If we had the components to figure this out, we would jump on it."

Martinez said his office is still waiting on three pieces of information needed to complete the valuation of the property.

In March — in a plea to Santa Fe County commissioners to increase the size of his staff — Martinez said there are numerous properties in the county that haven't been added to the tax rolls because of short staffing. Martinez said revenue generated by getting those houses on the rolls would far outweigh the cost of the new employees.

He mentioned to commissioners one property in particular that could be worth as much as $20 million and bring in as much as $140,000 worth of tax revenue annually. Martinez declined to name the property at the time, saying because it wasn't yet on the tax rolls, he couldn't discuss it.

Martinez said last week that staffers in his office have a stack of about 50 properties that they know need to be added to the rolls, but none are thought to be as highly valued as the Davis house. An unknown number of others could also likely exist, he said.

Before construction began on the home of Andrew Davis, who is president of the Davis Selected Advisors investment firm, it was a subject of controversy.

Some area residents protested the siting of the home on a prominent ridgeline, saying it violated city escarpment ordinances designed to protect views of Santa Fe's foothills. City officials granted a permit for the home, saying there were no other buildable locations on the steep lot.

When the county sent out notices of value this spring, the 11-acre site was listed as vacant property worth about $1.5 million, with an estimated taxable value of $500,000.

According to the property tax calculator on Santa Fe County's Web site, the tax liability on the property as currently listed is about $13,700.

According to the Web site, if a home is valued in the neighborhood of $5 million, the tax liability would be about $30,000 per year. If it is valued closer to $10 million, the calculator estimates the liability at about $65,000.

Martinez said he's hopeful the home's value can be determined before tax bills are mailed in November. Even if it is not, he said, the owners will still be legally responsible — eventually — for paying the 2009 taxes for the improvements on the property. "They aren't going to escape the tax for 2009," Martinez said.

The Davises did not return calls seeking comment. But Herdman said they aren't trying to shirk their tax bill. "The Davises intend to pay all of the property taxes that are due and owing on the property," he said. "They have cooperated with the Assessor's Office and will continue to cooperate as they have been doing since last September."

Contact Phaedra Haywood at 986-3068 or phaywood@sfnewmexican.com.