This paper proposes the use of a one-dimensional (1D) structural theory to analyze thin walled structures with longitudinal and transverse stiffeners. The 1D theory has hierarchical features and it is based on the unified formulation (UF) which has recently been introduced by Carrera. UF permits us to introduce any order of expansion (N) for the unknown displacements over the cross section by preserving the compact form of the related governing equations. In this paper the latter are written in terms of finite element matrices. The same 1D structural theory is used to model a given thin-walled structure composed of stiffened (longitudinal and transverse) and unstiffened parts. It is shown that an appropriate choice of N permits us to accurately describe strain/stress fields of both transverse and longitudinal stiffeners. Comparisons with available results from open literature highlight the efficiency of the proposed model. Moreover, a set of sample problems are proposed and compared with plate/shell formulations from a commercial finite element (FE) software.