I went through much the same process a few years ago. We had gotten a building permit for a shed that we were having built in the back yard. Some months later the assessor came by while we were on vacation and called so he could ask a few questions before he filed his official assessment. By the time we returned from vacation and got his message, he had already filed the assessment. He recommended that if the we thought that the assessment was too high, we should file an appeal and request a hearing before the Board of Equalization. I asked about the hearing thinking that it was something I would have to take the hassle of attending, but the assessor indicated that in my absence they would review the documents I had previously submitted, and that their ruling would cause the adjusted assessment to be locked in for three years, whereas if you stop short of requesting the hearing before the Board of Equalization, then the reduced assessment from the appeal is only valid for one year.

When we got the assessment some months later, the house was indeed reassessed to a value that seemed high. I contacted the county to get their official documentation for all of the houses on our street (about 16 houses, for which they charge some nominal fee like $0.50 for each). Sure enough, our house had the highest assessed value on the street. Of the other houses on the street, I found one with the most similar features to mine in those county records I had ordered (near identical square footage and lot size, same number of bedrooms and bathrooms, etc.). That house had sold within the prior year for significantly lower than the assessed value on our house. My appeal was based solely on this one other house similar to your situation. When the results of my initial appeal arrived, it included a form where you could check a box indicating that you wanted a hearing before the Board of Equalization. I checked that box and did nothing more. A few months later, I got the results of that hearing where the Board of Equalization knocked another few hundred dollars off the assessment, and indeed the assessed value remained fixed for the following three years.

I don’t know how that three year lock-in works in a situation where house values are declining, but it sure was great when house values were on the rise. If you don’t request the hearing before the Board of Equalization, I wouldn’t be surprised if you find that your reassessments over the next three years will be higher every year.