In this paper, an experimental investigation on the behaviour of 3D sandwich beams under transverse loading is reported. In order to study the shear strength, modes of failure, ductility and service ability, eight sandwich beams were tested at low shear span-To-depth ratio. Since the width and span are the primary variables, two different span-To-depth ratios, (LnID), 1.73 and 4.07, and four different depth-To-breadth ratios 1.13,1.44,1.62 and 1.92 were adopted at constant depth. In addition, the concrete cover on either face (vertical) of the polystyrene was kept constant with varying thickness of polystyrene inner layer. All the beams failed due to either flexure or diagonal splitting. Since the beams in this study were not provided with additional longitudinal tension reinforcement, only a major flexural crack was propagated which predominantly tended to split the beam into two. From the ratio of measured-To-predicted shear strength, it is concluded that ACI 318-08, IS 456-2000 and Eurocode 2 overestimate the shear capacity of sandwich beams. By incorporating the influencing parameters, ACI building code shear strength expression has been modified, which showed good agreement with the experimental results.