ST. LOUIS COUNTY • The median value of a residential property in St. Louis County declined 7 percent over the last two years, according to preliminary reassessment figures released Monday by County Assessor Jake Zimmerman.

Meanwhile, many properties in areas with high levels of foreclosure sales are down 12 percent or more, the figures show.

The county reassesses its property values every odd-numbered year. The last reassessment was conducted in 2011, and overall residential property values dropped about 4 percent that year.

This year, assessments increased for residential properties in only one school district — Clayton — but by just 0.4 percent. The assessments in other districts dropped anywhere from -0.2 percent (Kirkwood) to -24 percent (Riverview Gardens). Commercial values remained flat or dropped slightly.

Zimmerman said that sales volumes were picking up and that the real estate market appeared to be recovering. But values have not returned to their pre-recession levels.

“Our economy still has some work to do before the majority of property values begin rising again,” Zimmerman said in a statement. “While some individual properties and neighborhoods have seen value increases, most of St. Louis County real estate has continued to experience declines.”

The values released Monday are preliminary and can be changed by the assessor’s office until July 1. But Zimmerman’s office encouraged property owners to review their values as soon as possible.

The 2013 preliminary real property values can be viewed online at http://revenue.stlouisco.com/ias. Official notices of assessment changes and projected tax payments will be available on that site on May 31. Notices will be mailed at that time, but only to people whose values are increasing.

Residential property owners who believe there is an issue with their preliminary values are advised to schedule an informal conference with the assessor’s office. Residential property owners can call 314-615-4595 starting Wednesday to request an appointment. Appointments are limited.

In addition, the county is providing property owners with the help of advocates, free of charge. The advocates are real estate professionals who contract with the county to offer advice on appealing property values. Call 314-615-4611, or send an email to Advocate@stlouisco.com.

Those without access to the Internet, or who have questions after viewing their preliminary assessment online, should call the assessor’s office; residential property owners can call 314-615-4500, and commercial property owners can call 314-615-4984.

Paul Hampel covers St. Louis County for the Post-Dispatch.

Paul Hampel is a reporter for the St. Louis Post-Dispatch.