Understanding Substantial Damage in the International Building Code, International Existing Building Code, or International Residential Code

This document explains the criteria and process for determining Substantial Damage (SD) under the International Building Code (IBC), International Existing Building Code (IEBC), and International Residential Code (IRC), particularly for buildings in flood hazard areas. It details how SD triggers compliance with current floodplain management regulations and flood provisions of the I-Codes, and outlines the financial thresholds and calculation methods for SD and Substantial Improvement (SI). The guidance is intended for use in FEMA Public Assistance-funded repair or replacement projects, covering both residential and non-residential buildings. It also addresses the roles of local officials, cost estimation, and the relationship between SD/SI and eligibility for Public Assistance funding.