XI, 405.07: Gross Building Area (06/30/02)
Gross building area, which is the total finished area (including any interior common areas, such as stairways and hallways) of the improvements based on exterior measurements, is the most common comparison for two-family to four-family properties. The gross building area must be consistently developed for the subject property and all comparables that the appraiser uses. It should include all finished above-grade and below-grade living areas, counting all interior common areas (such as stairways, hallways, storage rooms, etc.), but not counting exterior common areas (such as open stairways).
We will accept the use of other comparisons for two-family to four-family properties (such as the total above-grade and below-grade areas as discussed above in Section 405.06), as long as the appraiser explains the reasons he or she did not use a gross building area comparison and clearly describes the comparisons that were made.