Before anyone can buy a house with a loan from a bank or refinance a mortgage, the lender needs an objective assessment of the property’s value — after all, the home is the bank’s collateral for the loan. Assessing the value is the job of the appraiser.

Appraising a home, particularly in New York City, is not simple. Similar apartments just a few blocks from one another can have very different values. The floor that a home is on, the kind of view or light it gets — each factor contributes to its value. The best appraisers are intimately familiar with the neighborhoods they work in.

Jonathan J. Miller, the president of the real estate appraisal firm Miller Samuel, says that with a co-op, he begins by examining the building’s financials: if there is likely to be an increase in maintenance or a special assessment, it might lower the appraisal.

Apartments on higher floors are generally worth more than those on lower floors, particularly when they clear the tops of surrounding buildings, thus affording better views and more privacy, he says. Appraisers record the square footage, the number of bedrooms and bathrooms, and other basics, but they also consider the overall condition, deeming it poor, fair, average or good.