As prefabrication of timber structures in the construction sector becomes part of the solution to overcome the housing and environmental crisis, the lack of efficiency of this industry needs to be addressed. This inefficiency, characterized by low production capacity, high costs, and large workforce, are in part due to the low adoption of automation and robotic technologies, caused by insufficient knowledge and research measuring the impact of these technologies. This paper aims to measure the efficiency of introducing automation in a prefabrication environment of timber-frame structures, through a decision analysis tool. Four layout types with varying automation levels are explored using simulation modeling, while KPIs are exploited to measure the efficiency of each production environment. A sensitivity analysis is conducted to assess the most performing layout if a new type of wall, requiring fewer tasks, is introduced in the product mix. A design of experiments (DOE) is also performed on the fourth layout, a fixed robotic cell with the highest level of automation, to assess the most influential variables. Results show a positive increase in worker, space, and production efficiency as the level of automation increase. This research contributes to the body of knowledge by providing a decision analysis tool supporting the choice of an optimized layout for the prefabrication of timber-frame walls (TFW). The findings and the decision analysis tool should provide solid grounds for future exploration of automation and practice in the field.