Every property in Webster County — all 34,000 parcels — is assessed by the Webster County Assessor’s Office.

When a new home is built, for example, the Assessor’s Office will send field appraisers to the home to measure it and get all the information needed to determine a valuation.

“We look at square footage, that’s the main one,” said Webster County Assessor Angie Vinson. She said a lot of people think the number of bedrooms has a large influence over the valuation, but really it’s the square footage that weighs heavily on the final number.

The Iowa Department of Revenue issues a Real Property Appraisal Manual that gives the formulas to calculate the property’s value using the data and variables assessed by the appraisers.

Appraisers will also look at the number of bathrooms, as well as the quality of the fixtures and finishes in the house. Other things like whether the basement is finished or unfinished, and if there’s a porch, patio, deck or garage factor into the final valuation.

“A lot goes into it,” Vinson said. “And I know a lot of people think that we just pull a number out of the sky, but we do go out and measure and we use the [Department of Revenue’s] Real Property Appraisal Manual [to calculate it].”

Each year, the Assessor’s Office uses information from building permits collected by municipalities and “drive by” assessments to update the assessed value of properties in the county. Then, every odd year, the Assessor’s Office does an “equalization” that adjusts the assessed values using property sales data.

By law, the assessed values of properties must be at 100 percent of market value, plus or minus 5 percent. So when properties are sold for higher prices than their assessed values, the assessed values of similar homes in the area will increase to meet that market value. Assessed home values will fluctuate as the housing market goes up and down.