What is not included in the square footage of a house?

Under ANSI Z765, the square footage of a house leaves out garages, unfinished space, anything below grade, and outdoor areas like porches, decks, and patios. Space with ceilings too low to meet the height rules is left out too.

A few exclusions surprise people. A finished basement is not included, even a walkout, because part of it is below ground. Neither is a three-season porch, a finished room you can only reach through the garage or by a pull-down ladder, or the open air above a staircase or two-story entry.

Excluded does not mean ignored. The appraiser still measures most of these spaces and reports them on their own lines, such as basement area, garage space, and porches, and they can still add value. They just stay out of the single living area number used to compare similar homes.