The Federal Insurance and Mitigation Administration recognizes policyholders who have maintained continuous coverage or have built in compliance with the Flood Insurance Rate Maps (FIRMs) - or who have done both - with grandfather rules that lower flood insurance rates. It works like this: If a policy was obtained prior to the effective date of a community's initial FIRM or before a flood map change, the policy holder is eligible to have a flood insurance policy rated using the prior zone and base flood elevation, as long as continuous coverage is maintained. Proof of coverage must be submitted to the insurance company. The flood insurance policy can be assigned to a new owner at the option of the policyholder when the structure is sold. If a building was constructed in compliance with a specific FIRM, the owner is always eligible to obtain a policy using the zone and base flood elevation from that FIRM, provided that proof is submitted to the insurance company. Proof of compliance includes documentation that the lowest floor level hasn't changed since it was built, and the building hasn't been substantially improved. (FEMA, Grandfather Rules, Jan 23, 2008)