DC Real Property Database = An INCORRECT building date

I just got an inquiry from a potential client that conveyed to me the the building date of her house, gleaned from the DC real property assessment database (under view property features). She said her house was built in 1900. The problem is, about 80% of the "built in" dates on the DC real property tax assessment database are just educated guesses, done by an assessor about 50 years ago. That's why the vast majority of the dates provided are even numbers! 1900, 1905, 1910, etc. I've researched houses that have had the date off by 90 years or more.

Unfortunately, real estate agents use these "constructed in" date as fact. That can lead to trouble, and I was involved as a consultant in one case in Georgetown where the RE agent told the buyer that house was built in 1835. Turns out, the house was built in 1935. In Georgetown, where the oldest house wins, that spelled embarrassment and a lawsuit.

So, please don't believe the assessment database. I wish they would simply remove the dates altogether, as they are almost completely useless and mostly inaccurate. They only way to tell is to have your house history researched and carefully documented from the original building permits that began in February of 1877, or by using a combination of maps, tax, and deed research for properties before 1877.