The Building Department maintains some building files on-site at City Hall and also maintains an off-site archive. The most efficient way to request information would be to fill out the Archive Search Request Form (PDF). On-site files can typically be made available within one business day. Requests that require a search of the archives are typically conducted once a week (usually on Wednesdays).
It is free to request an archive search and to view building files. If you wish to have files scanned or copied, that can be done for $0.50 per page and/or $4 a sheet. Requests for copies of large plans or plans in poor condition due to age may be sent to Ellis Art and Engineering for duplication and are billed to the applicant at their current rate. Copying and scanning can generally be completed within 10 days of the request.
Oftentimes the information the City has on file is quite limited, but other resources are available within walking distance of City Hall. Researchers may have luck conducting additional searches at the Humboldt County Library (1313 3rd Street, Eureka) or the Humboldt County Historical Society (703 8th Street, Eureka). If you own the property for which you are seeking information, the Humboldt County Assessor's Office (825 5th Street) may also be an excellent source of information.