Canada is beginning to shift towards the reuse of existing structures to reduce environmental impacts [5]. This shift has created a new culture of structural conservation and the need for engineers to understand the procedure of structural assessment of existing buildings. Historical structures are a specific niche of existing structures that require a closer assessment. Many historic structures in Canada are deemed unsafe and are closed or of limited access to the public. An “unsafe” steel and concrete heritage building rebuilt between 1929 and 1933, known as the absorption building, has been analysed structurally with respect to the National Building Code of Canada (NBCC) and the Standards and Guidelines for the Conservation of Historic Places (SGCHP) [7] [4]. The building is located at the Turner Valley Gas Plant (TVGP) National Historic site [8]. The TVGP was Alberta’s first natural gas plant built and thus the birthplace of the energy sector in Western Canada [8]. Throughout the building lifespan the structural skeleton has been adapted to accommodate changes in the oil and gas processing. The load path, effects of modified and missing members, and capacity of elements were assessed. Due to a lack of historical records and the building designation, Non-destructive and Minor destructive testing methods were used to determine building geometric and material properties. Five finite element models were developed to conduct a linear-elastic analysis of the buildings structural integrity. A load test was performed to validate the models. Results confirmed the load path and the effects of modifying members as an initial assessment towards a complete safety analysis. Based on the NBCC if the past performance of the structure is considered insufficient and a structural analysis is conducted the results show plastic hinges will begin to form in the roof of the structure due to the applied loads. The research exposed gaps within current NBCC and SGCHP guidelines. Technical testing and clarification on the potential interpretations of the NBCC and SGCHP are recommended additions based on the research conducted. As standards are developed the research provided can guide future engineers on conducting a structural safety analysis of heritage structures.