How are stairs to an unfinished basement calculated in the square footage of a house?
The American National Standards Institute’s ANSI-Z765-2003, Square Footage—Method for Calculating, states, “stairs that descend to an unfinished basement are included in the finished square footage of the first level.” The publication, which is the industry standard for calculating residential square footage, can be downloaded from the NAHB Research Center website for $10 at www.nabhrc.org/bookstore. The standard is not applicable to apartment/multifamily buildings and does not cover room dimensions.
