Modular construction has become increasingly popular in North America in recent years. In this emerging paradigm of building construction, building components are manufactured off site and then transported to the construction site for assembly. In Canada, automated modular steel structure fabrication is in high demand. Offsite manufacturing of steel wall frames for residential and commercial buildings provides timesaving and improvement of working conditions and morale that translates to improved productivity and safety performance. This paper demonstrates the feasibility of efficiently fabricating steel wall frames for offsite modular construction using automated assembly controlled by a Programmable Logic Controller (PLC) and connected in a cost-effective and efficient electrical installation and centralized communication by Fieldbus technology. In particular, this paper describes the control strategy used to automate a steel wall framing assembly that incorporates a PLC and Fieldbus technology.