Finding 'Comparables' on $100 Million Mansion

The Santa Clara County Assessor's Office is required to determine a fair market value for all properties for the county's assessment roll. That includes . 

They came up with a cash value that was . 

They applied the process is the same process as they do do for any other home in the county, "We didn't treat it any differently than a condominium in East San Jose," said Assessor Lawrence E. Stone. 

Of course, the process was much more complex than the average assessment. 

Most of the time, when homes are sold on the open market, the assessed value is the sales price. But this home wasn't sold on the open market.

"One sale does not make the fair market value," said Deputy to the Assessor David K. Ginsborg. The Assessor's Office sent appraisers to the home. Three appraisers have to make independent assessments of the property. "We have an extensive review process. Plus we look at comparables," Ginsborg said. "We scoured to learn more about those properties. That's the job of the appraiser."

"There are not that many transactions of mansions for a property of that magnitude," Assessor Stone said.  

Here's an example of the "comparables" that the assessor's office used:

• 30,000 sq. ft. mansion on 7.5 acres in Los Altos Hills — sold for $28.5 million
• 18,000 sq. ft. estate on 4.8 acres in Los Altos Hills — sold for $25 million (listed for $31 million)
• 11,000 sq. ft. historic mansion on 12 acres in Atherton  sold in September 2001 for $53 million (San Mateo County 

Largest Estate Listings

• 38,849 sq. ft. mansion on 6.7 acres in Hillsborough — listed for $43 million
• 14,000 sq. ft. estate on 4 acres in Woodside — listed for $43 million (San Mateo County; just canceled)
• 35,000 sq. ft. estate on 5.9 acres in Hillsborough — listed for $29 million (San Mateo County)
• 16,000 sq. ft. mansion in Pacific Heights area of San Francisco — listed for $28.5 million (San Francisco County)
• 5,850 sq. ft. estate on 3.4 acres in Woodside — listed for $19 million (San Mateo County)
• 8,285 sq. ft. estate on 11.61 acres, Portola Valley -- listed for $25 million (San Mateo County) 
• 13,459 sq. ft. estate on 7.88 acres in Saratoga -- listed for $16.7 million (Santa Clara County) 
• 56,500 sq. ft. Aaron Spelling Manor in Los Angeles — sold July 2011 for $85 million (Los Angeles County)