Thin-walled cold-formed steel represents a competitive solution for a wide range of structural applications due to its efficient use of materials and its rapid manufacturing and installation. Concerning the purlin systems, continuous Z-shaped steel purlins with overlapping over the intermediate supports are the best choice to minimise material use. The connection between two purlin segments can be achieved by overlapping the profiles over the supports. Starting from the outcome of numerical investigations done by the authors, using a finite element model validated against experimental data, an extensive study was performed to identify the parameters that influence the design of overlapped purlins under gravity and uplift loading. The analysis was performed on a two-span continuous beam with overlapping at the intermediate support. To capture as much as possible the real behaviour of the purlin, the sheeting was included in the model. The design of lapped purlins was found to be primarily influenced by the length of the span and the overlap length. The detail of the lapped connection is relevant only for short overlaps. The paper presents an experimental program on purlins with overlapping under the intermediate supports, under gravity and uplift loading. Two dimensions of the cross-sections are tested, i.e. Z200 and Z250 and symmetric overlaps (Lp1=Lp2): 100 mm, 300 mm, 450 mm, 600 mm, 900 mm and 1200 mm. The experimental testing is focused on identifying how different design assumptions will influence the behaviour of lapped purlins.