This study explores the problem solving strategies used to solve challenging problems when undertaking valuation of a commercial property. Verbal protocols were collected and analysed from six subjects of varying level of expertise (Novice, Intermediate and Expert) undertaking the task of valuation of a commercial property. The results showed that where available data is inadequate, valuers solve an overall valuation problem by dividing the problem into a number of sub-problems that are solved by integrating available data with existing knowledge through forward and retrospective (‘backwards’) reasoning. However, there were effects associated with level of expertise in the way the processes of forward and backward reasoning are used, with the expert and intermediate valuers being more thorough and comprehensive than the novice valuers. This enabled the expert and intermediate valuers to develop a greater number of more-sophisticated solutions to challenging valuation problems, Novice valuers could not generate such well-developed solutions indicating that they were much more superficial in their valuation problem solving. It is argued that, to develop adaptable expertise, training situations need to be provided which encourage the development of forward and backward reasoning within a functional context (required for non-routine problems). But there many challenges in designing courses to incorporate these features.