Compounding the issue is the reliability of the various sources. Many properties built after the big quake (a large portion of the City’s building records were destroyed in 1906) have a square footage figure on record with the city Assessor’s Office. However, many properties have no figure available and any figure that does exist may not include additions to livable space that have occurred since the original construction date.
There’s also human error to consider. Did the builder correctly note the square footage at the time of construction? Did the real estate agent transpose some of the numbers? What about the clerk in the appraiser’s office? Was the lot size accidentally inserted into the spot used for interior square footage? It’s all happened at one time or another!
The long and short of it is this: if square footage is important to you then don’t depend on the information that you are presented with. Get it checked! Fortunately, there are services available that specialize in property measurement that are reasonably priced and will tell you exactly how they arrived at the number that they deliver to you. Better to be safe. Right?