If the value of the addition or improvement to the residential structure is less than 50% of the market value of the existing structure, you need only make sure that the improvement meets or exceeds the standards that were used in constructing the existing structure (assuming the existing structure was built in compliance at the time it was constructed). Additions or other improvements valued at 50% or more of the market value of the existing structure are considered substantial improvements. In such cases, the entire structure must be brought into compliance with the elevations on the map in effect at the time the improvement begins.
Under certain circumstances, only the addition needs to be elevated to the flood elevations shown on that map. Please note, however, that there may be more stringent state or local requirements that take precedence over those stated here. Regardless of whether your building is substantially improved, you will likely need a building permit to make the improvement and need to contact your local building official.
Create a FIRMette of my property.