An expert system is applied to the design of industrial roofs. All the codal knowledge are considered in the design. The VP EXPERT shell is used to represent the knowledge in the form of rules. A database containing different sections and their properties are used in the design. Five different types of trusses are designed, using expert system and grouping the members into six regions. Three loading cases are considered in the analysis of the truss. The same five types of trusses are optimized using genetic algorithm. Design variables are the area of members and six variables with three bit length for each variable are taken. The stress and displacement constraints for the three loading cases are considered. The design results using the expert system compare favorably with results of genetic algorithm.