There are two alternatives for production organisation in precast factories, namely the comprehensive method and the specialised method. Production scheduling under the specialised alternative has been found to be a difficult optimisation problem if heterogeneous elements are involved. A flow shop sequencing model is developed for this kind of production scheduling that considers the constraints encountered in actual practice. The model is optimised using a genetic algorithm (GA) approach. The results are compared with those obtained using classical heuristic rules in two examples that involve the objective of minimising the makespan or the total tardiness penalty. The comparison shows that the GA can obtain good schedules for the model, giving a family of solutions that are at least as good as those produced by the heuristic rules.