The valuation for insurance purposes is generally not the current, depreciated value of the building, but the cost to rebuild, at today's material and labor prices, and with modern materials and systems.

A 50 year old building, with old systems, may be fully depreciated, but if one had to rebuild, one would need far more than the current building is worth.

When one buys a home with a mortgage, the bank requires an appraisal. In some places, the forms don't even break out land value from building value, or they do it badly. An appraisal merely compares the subject house with others that have sold recently in the same area. Better location? $15,000 more (or, in California, $100,000 more) Inferior location? subtract $15k or $100k. 1 more bathroom? Add $5,000 (CA: might be $5k or $50k) new kitchen vs 20 y/o kitchen? Add $10k, $50k or $100k, or more, depending on what is typically spent in that neighborhood. For each "comparable" add up all the pluses and minuses, and add that to the transaction price for that property. Average those, and the subject house value is estimated. Land value is in there, but not explicit.

California has assessors, too, who, after a property has sold, update the assessment on it to equal the transaction price. Some goes to land, some to the building. (check out listings at realtor.com, and fully expand the property history info. Notice when the previous transaction was, and look at the increases. They are in reality mostly land value. Buildings don't appreciate. Land rises and falls in value --- mostly rises.)

But appraisers and assessors are very different.