The work presented in this paper is considered to be an attempt to contribute towards a better understanding of the structural behaviour of plain concrete slabs under step loading conditions. The Concrete Society Technical Report TR34 “Concrete Industrial Ground Floors” is in its 3rd edition (2003) and is currently under review. TR34 covers the design of concrete ground-supported slabs containing fibres, both steel and synthetic, as an alternative to mesh reinforcement. This work reports on tests carried out at different critical loading locations, including the centre, edges and corners of a 6.0 × 6.0 × 0.15 m deep plain concrete slab. The test results are compared with theoretical values derived using available design codes and other information sources. The results show a notable difference between the test results and the theoretical values.