Information about making Substantial Improvement Determinations for Proposed Development in the Special Flood Hazard Area
Before improvements to buildings located in the Special Flood Hazard Area
on FEMA flood maps
can be performed, NFIP communities
must determine if the building has been Substantially Improved. This is a formal determination of whether the cost of repairs and improvements will equal or exceed 50% of the market value of the structure before the improvement.
If proposed improvements are determined to be a Substantial Improvement (SI), the building must meet the same requirements in the community’s floodplain ordinance that apply for new construction. Communities may choose to adopt a higher standard (e.g., using a lower percentage to make the SI determination or adopting a cumulative SI provision) to further improve flood resilience in the community.
There are exceptions to the SI provision that apply for alterations of designated historic structures and corrections of existing code violations, as outlined in the community’s floodplain ordinance.
SI Determination Process for Community Officials
The steps that must be performed by communities to make an SI determination include the following.