Addition of storeys to a house

The project is about a single-storey building built in 2000. The load assumption for the structural design loads  predicted the addition of 3 extra storeys. The present owner  wants to build 3 additional storeys and a roof addition. The complexity of the design lies on the fact that the original 1999 design didn‘t comply with the anti –seismic standards. 

The additional structure will be a steel structure with composite slabs . The columns will be extended into the foundation and through the 1st Floor.

The two structures are completely independent.