This paper presents a probabilistic approach for mechanical design problems and applies this approach to a fusion reactor first wall design analysis. The method developed is based on Response Surface Methods, developing an approximation to a consequence of interest. A probability distribution for the consequence is found by Monte Carlo sampling of the input parameters probability distribution and then using the response surface. Adopting a defined criteria for failure, a probability of the consequence exceeding the criteria is found. In this paper the method is applied to the examination of neutron wall load implications. The motivation for this work is to provide an additional tool for design development and assessment.