Substantial Damage and Substantial Improvement

House with flooding


When a structure in the SFHA is more than 50% modified (damaged and repaired or improved), the structure must be brought into compliance with NFIP requirements and local floodplain ordinance standards.  Modifications can come after disasters such as floods or wildfires or they can happen when a structure undergoes general repairs or improvements.  Any modification to a structure in the SFHA is an opportunity for structure owners and floodplain management programs to reduce future risk of flooding or otherwise.

What is Substantial Damage?

Damage of any origin (ie. Flood, fire, tornado, etc) sustained by a structure whereby the cost of restoring the structure to its pre-damage condition would equal or exceed 50% of the market value of the structure before the damage occurred.

What is Substantial Improvement?

Any reconstruction, rehabilitation, addition, alteration or other improvement of a structure in which the cost equals or exceeds 50% of the market value of the structure before the “start of construction” of the initial improvement.  Includes  structures which have incurred “substantial damage.” regardless of the actual repair work performed.

What is the 50% Rule Determination?

City of Murfreesboro officials (typically the Floodplain Administrator) is responsible for substantial improvement/substantial damage (SI/SD) determinations. These determinations are required to be in compliance for participation in the NFIP.   (SI/SD) using the following procedures:

  • Review the permit application and compare the value of construction to the value of the structure.
  • If the cost of improvements exceeds 50% of the assessed value
  • Existing buildings that are deemed substantially damaged or improved must be brought into compliance with the current requirements of the Section 34 Floodplain Zoning Ordinance.