Residential Appraisal

The County is responsible for appraising all urban and rural residential properties.  A mass appraisal method is used to appraise all residential properties following the rules and procedures in the Department of Revenue's publication, Appraisal Methods Manual.  In addition, we use cost factor books published by the Department of Revenue to determine the base cost of structures; Cost Factors for Residential BuildingsCost Factors for Manufactured Structuresand Cost Factors for Farm Buildings.

After passage of Measure 50 in 1997 which significantly changed Oregon Property Tax Laws, it was believed that real market value was not as important as it was previous to 1997 since most properties would be limited to a 3% growth in their newly established maximum assessed value.  The real market value would continue to be market trended based on actual increase or decrease in the real estate market.  The tax assessed value is the lesser of the maximum assessed value or the real market value.  The mandate to reappraise all property every six years had been removed and the staffing levels in many of the county assessor's offices through the state was reduced.  However, in practice it was determined that real market value does have a large effect on taxable assessed values, particularly during a declining market where many property owners pay tax based on their real market value rather than their maximum assessed value.  In addition, many new structures were not placed on the tax rolls due to either no permit issued or permits that were never received by the Assessor.

During 2006 and 2007, Columbia County converted to a new assessment and taxation system capable of 'recalculation', which maintains real market value more accurately each year than just a market trend adjustment.  In order to take full advantage of the program, detailed inventory data must be entered for each property.  Since it had been at least 15 years since one of the six maintenance areas in the county had been physically inspected, we developed a limited (curbside) inspection process to begin capturing the inventory and noticable changes to properties in order to complete one maintenance area each year with limited staffing and resources.  Advanced notice is not given prior to inspection, however, for properties with major changes, appraisers will attempt to contact the owner and/or complete a full exterior inspection.  As of 2017, all areas of the county have been reappraised using the limited inspection method, and all residential properties are subject to annual recalculation.

Recalculation requires an annual setup of land values, local cost factors and depreciation schedule for each area that has sufficient data entered in the system.  Values are then electronically recalculated using the new factors without a physical inspection.  These setups are completed using sales data prior to the assessment date of January 1, so an additional market trend study is done later to further adjust the recalculated value based on the actual market.  Areas that are not yet able to be recalculated have only a market trend study completed to adjust the previous year value to the current year.  For 2018, a summary of the analysis and conclusions has been published and is available for download here.

Our plan is to reappraise properties in each area with limited exterior inspections once every seven years in order to continue placing non-permitted structures on the tax roll and removing demolished structures, as well as to adjust properties due to better or worse condition than the previous cycle year.  Areas that are not being reappraised will continue to be recalculated using the factors developed in our annual recalculation and reappraisal setup study.


Frequently Asked Questions

230 Strand St.
Columbia County Courthouse Annex
St. Helens ,
Fax: 503-397-5153

Monday - Friday
8:30 a.m. to 5:00 p.m
We are closed the second Thursday of each month from 8:30 a.m. to 12:00 p.m. for staff work sessions and training.
Sue Martin