In this paper a general design method is described that can significantly reduce the effort needed for form finding grid shells consisting of flexible members. This design method is based on particle-spring models for simulating the behaviour of a grid shell during construction. Hereby, the stress limitations that follow from the material properties are taken into account to modify the grid shell geometry with a minimal deviation from a pre-defined target shape. It is demonstrated how a simple design tool can generate the geometry, internal forces and the support reactions with satisfactory accuracy.