It's a document typically prepared by a registered land surveyor and used to establish that the house was properly elevated as required by Federal and County flood plain management regulations.  The floor elevation listed on the certificate is typically that of the lowest habitable floor elevation of a structure.  The elevation value is in "feet above mean sea level".  The form used for certificates has changed significantly over the years.   Elevation Certificates were first required for houses on property located in the FEMA 100 Year Flood Zone and permitted after August 1, 1980.   We have on file thousands of certificates for nearly every house built since August 1980.  Please note that occasionally we are unable to locate some certificates due to erroneous addresses or filing/handling errors.