The paper studied the rehabilitation and increase in height of an existing 30 ft tall, industrial, guyed steel stack, which was built around 1977. The stack is supported on an industrial building. Stacks are an essential part of the industrial facilities. They allow the discharge of chemical waste gases from industries to the atmosphere, under stringent pollution control guidelines. The height of the stack is increased by 40 ft to comply with the new guidelines. Analytical and numerical simulations were performed using MecaStack software (local model) and SAP2000 V.20 software (global model). Analysis and design are based on the ASME STS-1-2016 standard code. Discontinuity around the manhole at the bottom of the stack is investigated with SAP2000 V.20 finite element software. Results in terms of principle stresses, and Von-Mises stress, were used to prepare recommendations, repair and construction documents for the project.