This paper addresses the design and fabrication of non-uniform structural shell systems. Structural shells, particularly gridshells, have a long history but due to their complexity and the accompanying high cost of construction, their application has been limited. The research proposes a method for integrating the design and fabrication processes such that complex double curved reticulated frames can be constructed efficiently, from prefabricated components, requiring significantly less formwork than is typical. A significant aspect of the method has been the development of software tools that allow for both algorithmic form-finding and the direct control of robotic fabrication equipment from within the same modelling package. A recent case-study is examined where the methodology has been applied to construct a reticulated shell structure in the form of a partial vault. Components were prefabricated using 6-axis robotic fabrication equipment. Individual parts are designed such that the assembly of components guides the form of the vault, requiring no centring to create the desired shape. Algorithmically generated machine instructions controlled a sequence of three tool changes for each part, using a single modular fixture, greatly increasing accuracy. The complete integration of computational design techniques and fabrication methodologies now enables the economical deployment of non-uniform structurally optimised reticulated frames.