Substantial Improvement/Substantial Damage Desk Reference
To participate in the National Flood Insurance Program (NFIP), communities must adopt and enforce regulations that apply to all development in Special Flood Hazard Areas (SFHAs).
Specifically, local floodplain management regulations must contain minimum NFIP requirements that apply not only to new structures but also to existing structures that are “substantially improved” (SI) or “substantially damaged” (SD). Those NFIP requirements are set forth in the Federal Emergency Management Agency (FEMA) Federal Regulations. The SI/SD Desk Reference provides guidance and suggested procedures to assist states and communities in implementing those NFIP requirements.
Implementing Substantial Improvement/Substantial Damage Requirements Locally
When buildings undergo substantial repair or improvement, it is an opportunity for the local floodplain management program to reduce flood damage exposure to existing structures. Communities participate in the NFIP by adopting and enforcing regulations and codes that apply to all development in SFHAs.
Local officials in communities that participate in the NFIP must determine whether proposed repair work or upgrades meet the definition of a substantial improvement or substantial damage (referred to as an “SI/SD determination”) building. If work on buildings constitutes SI/SD, structures must be brought into compliance with NFIP requirements for new construction, including the requirement that lowest floors be elevated to or above the base flood elevation (BFE). The NFIP defines SI/SD as follows:
Substantial improvement (SI) means any reconstruction, rehabilitation, addition, or other improvement of a structure, the cost of which equals or exceeds 50 percent of the market value of the structure (or smaller percentage if established by the community) before the “start of construction” of the improvement. This term includes structures that have incurred “substantial damage,” regardless of the actual repair work performed.
Substantial damage (SD) means damage of any origin sustained by a structure whereby the cost of restoring the structure to its before-damaged condition would equal or exceed 50 percent of the market value of the structure before the damage occurred. Work on structures that are determined to be substantially damaged is considered to be substantial improvement, regardless of the actual repair work performed.
This Desk Reference is designed for local officials who are responsible for the administration of local codes and regulations, including the SI/SD requirements. It also is intended for State officials who provide technical assistance to communities on the NFIP. The document provides guidance on the minimum requirements of the NFIP regulations.
Having a Community Commitment To Floodplain Management Can Lower Flood Insurance Costs
Remember, FEMA encourages communities to consider “going one step further.” States and localities may adopt requirements that are more restrictive, and if so, these take precedence over less restrictive requirements. This is often referred to as “exceeding the NFIP minimums” or “higher standards.”
If a community does choose to adopt higher standards, they may be eligible for participation in the NFIP Community Rating System (CRS). Joining the CRS and having an active commitment to safer floodplain management practices like this can lead to insurance discounts for residents. See our recent eWatermark articles about the benefits of the CRS Benefits from Community Floodplain Management Activities through the NFIP Community Rating System and Answers to Questions about the National Flood Insurance Program’s Community Rating System.
Other Sources for Building Code Guidance
Keep in mind that floodplain management is only part of your State and local building code system. The following resources may be useful in the process of ensuring your residents’ continued safety:
- NFIP State Floodplain Coordinator. Each State has a designated State Coordinating Agency for the NFIP, with an individual identified as the NFIP State Coordinator. State Coordinators provide a link between the Federal Government and local governments on matters related to floodplain management. You can find out more from the Association of State Floodplain Managers (ASFPM) at the FloodSmart Website.
- International Building Codes. Many States and communities have adopted one or more of the codes in the family of codes published by the International Code Council, Inc. (I-Codes®) or use the I-Codes as the basis of their own codes. These codes contain provisions for buildings in flood hazard areas, including provisions related to substantial improvement and substantial damage. The pertinent codes are the International Building Code® (IBC®), International Residential Code® (IRC®), and International Existing Building Code® (IEBC®). Each references Flood Resistant Design and Construction (ASCE 24-05), the national consensus standard produced by the American Society of Civil Engineers, Inc. (ASCE).
- The FEMA Building Sciences Branch. Rebuilding homes or businesses after a disaster is the right time to incorporate techniques to prevent future disaster damages. The FEMA Flood Insurance and Mitigation Administration Building Sciences Branch can provide comprehensive information on the destructive forces of certain hazards and techniques for building disaster-resistant structures. Additional resources, free publications, and design guidance can be found through the Building Science Branch.
For more information:
FEMA P-758, The NFIP Substantial Improvement/Substantial Damage Desk Reference.
FEMA 213, Answers to Questions about Substantially Damaged Buildings is a FEMA publication that summarizes answers to certain key questions about substantial damage and a few questions related to substantial improvement.
Rebuilding homes or businesses after a disaster is the right time to incorporate techniques to prevent future disaster damages. The following resources provide in-depth information on the destructive forces of certain hazards and techniques for building disaster-resistant structures. Additional resources, free publications, and design guidance can be found through the Building Science Branch.
The NFIP Community Rating System