Pre-FIRM buildings are those built before the effective date of the first Flood Insurance Rate Map (FIRM) for a community. This means they were built before detailed flood hazard data and flood elevations were provided to the community and usually before the community enacted comprehensive regulations on floodplain regulation. Pre-FIRM buildings can be insured using "subsidized" rates. These rates are designed to help people afford flood insurance even though their buildings were not built with flood protection in mind.
Post-FIRM buildings are new construction and those built after the effective date of the first FIRM for a community. Insurance rates for Post-FIRM buildings are dependent on the elevation of the lowest floor in relation to the BFE.