(Amended by Ordinance No. 178831, effective November 20, 2004.) An addition that is not structurally independent from an existing building shall be designed and constructed such that the entire building conforms to the seismic force resistance requirements for new buildings unless the three conditions listed below are met. Furthermore, structural alterations to an existing building or its structural elements shall also meet the following three conditions:

 

A. The addition or structural alteration shall comply with the requirements for new buildings;

 

B. The addition or structural alteration shall not increase the seismic forces in any structural element of the building by more than 5 percent unless the capacity of the element subject to the increased forces is equal to or greater than that required for new buildings. Multiple force increases on an element are allowed provided the cumulative force increase does not exceed 5 percent of the force on the element from its original, unaltered state; and

 

C. The addition or structural alteration shall not decrease the seismic resistance of any structural element of the existing building unless the reduced seismic resistance of the element is equal to or greater than that required for new buildings.