Accuracy of <i>HAZUS</i> General Building Stock Data

Abstract

The accuracy of the Federal Emergency Management Agency’s HAZUS general building stock (HGBS), widely used to estimate potential monetary damage to building structures from floods, earthquakes, or hurricanes, is quantified by comparing HGBS square footage and replacement-cost values to corresponding data from building cost inventories previously compiled for three Midwestern locations. The HGBS data (released in 2015 based on year 2010 census data) underestimates all building square footage by between 15 and 20% and overestimates replacement costs by between 31% (without considering depreciation) and 56% (including depreciation). The magnitude of HGBS inventory differences vary across structure types, particularly among different classes of commercial structures, but are markedly consistent across the three locations. Because the HGBS underestimates structure size and overestimates replacement costs, it severely overestimates replacement costs on a dollar per square foot basis, on average by between 51 and 81%. These large overestimates could potentially occur with a partial or hybrid Level 2 HAZUS analysis, in which supplemental structural square footage is obtained from a non-HGBS source, such as a tax assessor, while using default HGBS building replacement cost data.