The flood maps for Key West first became effective December 31, 1974. Buildings constructed after that date were required to be at certain minimal elevations above sea level. Existing buildings within regulated flood zones were grandfathered into the National Flood Insurance Program (NFIP) at their current elevations. However, that grandfathered status ceases once the building has been renovated by half it’s market value. Once that threshold is reached, renovation plans must include elevating the home to current flood levels.
Actually, the first flood maps were effective circa 1970/71, back when the NFIP was administered by the U.S. Department of Housing and Urban Development (HUD) . When Federal Emergency Management Agency (FEMA) took over, it had great difficulty discerning records for the early years of the program. As a result, FEMA stipulated, that any community with flood maps having an effective date prior to December 21, 1974 - such as Key West - would now be governed by this 1974 date rather than the earlier map dates.