This paper experimentally and numerically studied the influence of interlayers on flexural performance of four-side simply supported laminated glass (LG) carrying uniformly distributed loads of 1 minute at 20 °C. The flexural stiffness of the LG using ionomer interlayer was found increasing with increasing interlayer thickness, while that of the LG using polyvinyl butyral interlayer was found insensitive to interlayer thickness. The strengths of the two types of LG can be enhanced by increasing interlayer thickness only in case the effect of large deflection was not significantly involved. The strengths of the two types of LG having interlayer thickness of 0.38 mm were found close to that of a monolithic glass having twice the thickness of each laminate glass ply. The results obtained were expected to provide useful information for academic and engineering professionals in analysis and design of LG plates sustaining medium term duration loads in room temperature.