A classified federal heritage building requiring structural rehabilitation of the existing building and the construction of a new freestanding mutli-story addition. This historic building was constructed in 1930 to serve as a multi-purpose government facility, to accommodate over 500 attendees. We were responsible for the rehabilitation of the existing building that included exterior masonry conservation, seismic upgrading to meet requirements of NBC 2010, revision to the existing structural framing to accommodate mechanical requirements. For new construction, a post-tensioned structural glazing façade, structural glass roof and cantilevered staircase with bridge were designed at the atrium space between the heritage building and the new addition. The major challenges involved the conservation approach to the design, which dictates minimum intervention. Sometimes, this philosophy is at odds with the need to meet the NBCC seismic requirements. This demanded an understanding of how the existing materials perform, and finding compatible solutions to satisfy the two opposing objectives.