Guides for Substantial Damage & Improvement

Local Official Guidance


Substantial Improvement/Damage Regulations

To participate in the National Flood Insurance Program (NFIP), communities must adopt and enforce regulations and codes that apply to new development in SFHAs.  Local floodplain management regulations and codes contain minimum NFIP requirements that apply not only to new structures, but also to existing structures which are “substantially improved (SI)” or “substantially damaged (SD).”  

Substantial Improvement Description

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 before the “start of construction” of the improvement. This term includes structures which have incurred “substantial damage,” regardless of the actual repair work performed. The term does not, however, include either:

  1. Any project for improvement of a structure to correct existing violations of state or local health, sanitary, or safety code specifications which have been identified by the local code enforcement official and which are the minimum necessary to assure safe living conditions or
  2. Any alterations of a “historic structure,” provided that the alteration will not preclude the structure’s continued designation as a “historic structure.”

Floodplain management requirements for new construction apply to substantial improvements. Increased Cost of Compliance (ICC) coverage does not apply to substantial improvements unless a structure is substantially damaged due to flooding.  Link to the federal NFIP requirement.

  • 3 – Flood plain management criteria for flood-prone areas
    • (b) (5) – Elevation Certificate
    • (c) (3) – A Zone Nonresidential Buildings
    • (c) (4) – Zone A Nonresidential Buildings
    • (c) (5) – Openings
    • (c) (6) – Zone A Manufactured Homes
    • (c) (7) – Zone AO Residential Buildings
    • (c) (8) – Zone AO Nonresidential Buildings


FEMA’s Substantial Improvement/ Substantial Damage Desk Reference


Download FEMA’s Substantial Improvement/ Substantial Damage Desk Reference.  This Desk Reference provides practical guidance and suggested procedures to implement the NFIP requirements for SI/SD. 

Link to the FEMA issued a SI/SD Desk Reference.


Temporary Occupancy of Substantially Damaged Structures after a Disaster

April 2018

This fact sheet is designed to help Floodplain Administrators and Building Code Officials understand whether communities may allow displaced property owners to occupy potential or declared Substantially Damaged (SD) residential structures until the structure can be brought into compliance with local floodplain management ordinances or building codes.  Downloadthe FSTempOccupancySubstantiallyDamagedStructuresAfterDisaster508.  For additional guidance on SD, see FEMA P-758 Substantial Improvement/Substantial Damage Reference (2010).


Understanding Substantial Structural Damage in the International Existing Building Code

April 2017

This document will help you understand how the concept of Substantial Structural Damage (SSD) is used within the International Existing Building Code® (IEBC®).  FEMA’s Public Assistance Required Minimum Standards Policy found in the Public Assistance Program and Policy Guide, Chapter 2 – Section VII.B.2,1 (Policy) requires that projects receiving FEMA assistance for repair or replacement incorporate the natural hazards-related provisions of the most recent edition of the International Code Council’s® (ICC®International Building Code® (IBC®), International Residential Code® (IRC®), and/or the IEBC.  The policy applies to buildings that have sustained any level of damage (including, possibly, SSD or Substantial Damage), as well as projects involving new construction, such as improved projects, alternate projects, or projects eligible for replacement in accordance with 44 CFR, Part 206.226(f).  The relevant code provisions include not only the design criteria for repair or replacement construction, but also those provisions that determine whether repair to the pre-damage condition is sufficient, or whether repair must be supplemented by improvement.  Download the PA_Job-Aid-Understanding_SSD_International-rev.


Substantial Damage Fact Sheet

October 31, 2016

  • Rebuilding after a flood provides an opportunity to make buildings stronger and safer.
  • Individuals, communities, businesses and government agencies all have a stake in how buildings damaged from a flooding event are built, rebuilt and repaired. The primary goal is to reduce risk of loss from future floods.
  • If local officials determine that a residential structure in the floodplain has been substantially damaged – meaning the cost to repair the home is equal to or greater than 50 percent of its market value before the flood damage – the owner generally has three options:
    • Elevate the building to a height determined by local officials;
    • Relocate the structure outside the floodplain, or
    • Demolish the structure.
  • Since floodplain ordinances are established at the local level, local and state officials may use different substantial damage percentages and different valuations as long as they are not below NFIP standards.
  • The local standards must be applied uniformly to all structures within their jurisdiction.
  • Local officials determine if a building in their jurisdiction has been substantially damaged.
  • FEMA does not make a determination of substantial damage and does not notify any property owner of a damage determination.  FEMA damage assessment teams may be asked to respond to local requests to assess the extent of disaster-caused damage to some structures. The data is provided to local jurisdictions, which may make substantial damage determinations based on their own ordinances.
  • FEMA mitigation experts have been and continue to be in close contact with local officials, especially floodplain managers, to provide detailed information and expert advice on repairing and rebuilding damaged homes in the floodplain.
  • Bringing homes and businesses into compliance with local floodplain ordinances is not only required, but may reduce individual flood insurance premiums.

Link to the Substantial Damage Fact Sheet.  


FEMA Releases Damage Assessment Operating Manual

March 31, 2016

The FEMA Damage Assessment Operating Manual establishes national damage assessment standards developed from lessons learned and best practices already in use and is intended to increase the accuracy, consistency, and efficiency of damage assessments by empowering emergency management at all levels with clear information and defined roles and responsibilities.  The Manual is aimed at clarifying FEMA damage assessment guidance, promoting standardized information collection, and assisting in the development of requests for federal disaster assistance.  The standards put forth in the manual will be the national standard utilized by states and tribes conducting damage assessments after disasters.  

The FEMA Damage Assessment Operations Manual is intended to expedite decision-making and the delivery of assistance by defining national standards for assessing damage and clearly outlining the information considered when evaluating requests for a Major Disaster Declaration.  To support this overall objective, this manual aims to achieve three major goals:

  1. Promote accuracy by clearly defining the information and documentation that should be collected to assess damage and support requests for Stafford Act assistance;
  2. Promote consistency by standardizing the criteria used to assess damage to residential homes and offering clear guidance on assessing damage to infrastructure;
  3. Promote efficiency by empowering emergency management at all levels with the structure and information needed to streamline damage assessment efforts.

Link to the FEMA Damage Assessment Operating Manual.


Substantial Damage Estimator (SDE) Tool (2017), FEMA P-784

FEMA developed the SDE tool to assist State and local officials in estimating Substantial Damage for residential and non-residential structures in accordance with the requirements of the NFIP as adopted by the communities.  The tool can be used to assess flood, wind, wildfire, seismic, and other forms of damage.  It helps communities provide timely Substantial Damage determinations so that reconstruction can begin quickly following a disaster.

The FEMA Substantial Damage Estimator Best Practices (2017) document suggests approaches for dealing with some of the challenging situations users may encounter while using the SDE tool.  After a disaster, the complexity of field conditions and the need to prepare for and perform SDE inspections to assess damage can present numerous challenges.  This document contains suggested solutions to some common challenges that SDE users may encounter.  The information and methods can be used by Federal, State, and local officials when developing SDE-based inventories of potentially substantially damaged residential and non-residential structures.  The guidance is organized into three phases of SDE management: 1. Planning for Data Collection, 2. Field Work, and 3. SDE Quality Assurance Reviews.

Although the SDE data collection and reporting process remains relatively unchanged from previous versions of the tool, the SDE 3.0 release focuses on enhancing the three key areas of performance, data accessibility, and usability.  Updates to the tool’s algorithms and some new embedded functionality create significant performance enhancements over previous versions.  Users can now access the underlying database to run queries, perform bulk updates of data, or generate custom reports using their own databases and reporting tools.  SDE 3.0 improves the user experience with dozens of enhancements that address user feedback.

FEMA P-784, SDE User Manual and Field Workbook: Using the SDE Tool to Perform Substantial Damage Determinations (August 2017), and the FEMA Substantial Damage Estimator Best Practices (August 2017) document have been updated to reflect the enhanced tool. 

Link to FEMA’s webpage to download different sections of the SDE.  

Link to


Substantial Damage Estimator Best Practices

SDE is designed to help Federal, State, and local officials manage data collection and assessment of substantial damage. Often the complexity of field conditions, limited access to technology, or inspection work in the field present situations that require additional organization and planning. This document contains suggested solutions to some common situations SDE users may encounter. The information and methods can be used by Federal, State, and local officials when developing SDE-based inventories of potentially substantially damaged residential and non-residential structures. The guidance is organized into three phases of SDE management: 1. Planning Data Collection, 2. Field Work, and 3. Data Management.

Link to the Substantial Damage Estimator Best Practices was developed to provide suggested approaches for dealing with some of the challenging situations users may encounter while using the SDE Tool.

Guides for Substantial Improvement/Damage

Follow the links …

Managing Floodplain Development Through the NFIP (pages 8-4 to 8-16) 

Substantial Damage Estimator (includes a user’s manual, workbook, and the software) (FEMA P-758)

Answers to Questions About Substantially Damaged Buildings, FEMA 213

Model Guide for Post Flood Damage Standard Operating Procedure

SI-SD Desk Reference Costs


SD Worksheets

Damage Inspection Worksheet Non-Residential

Damage Inspection Worksheet Residential


FEMA SDE Tool Frequently Asked Questions

Follow the links…








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