Grandfathering - To recognize policyholders who have built in compliance with the FIRM or remained loyal customers of the NFIP by maintaining continuous coverage, FEMA allows for optional "Grandfathering" of the NFIP flood insurance rate. When a new FIRM goes into effect and updates the flood zone and/or BFE for a building, the grandfathered rate can be based upon a prior flood zone and/or BFE as shown on a historical FIRM, if:

1. An NFIP policy was obtained prior to the effective date of a current FIRM, in which case the policyholder is eligible to maintain the prior flood zone and/or BFE as shown on the historical FIRM as long as continuous coverage has been maintained; or
2. Even when continuous coverage has not been maintained, if the building was constructed in compliance with the FIRM in effect at the time of construction and has not since been substantially improved, the owner is eligible to obtain a policy using the flood zone and/or BFE from that FIRM provided that documented proof that the property meets the qualifying conditions is submitted to the insurance company.