The Commission requested EFSA to assess three studies concerning the use of rubber slats in pig holdings regarding the statistical differences between the welfare outcomes for sows and gilts when comparing concrete slatted floors and floors with a rubber overlay. The appropriateness of the methods used was assessed with respect to objectives of the studies and minimisation of the risk of bias. Measures and methods of measurements applied in the studies were compared against animal-based and non-animal-based measures recommended in EFSA opinions. The risk factors and needs of different categories of pigs regarding flooring as outlined in EFSA opinions were compared. The validity of studies A and B is questionable because of the way the field experiments were performed and/or reported. Their results must be used with caution because of the risk of bias identified. The power of study B is possibly insufficient to detect any biologically relevant effects. Studies A and B only partially use welfare measures that are relevant for assessing the degree of compliance with the legal minimum requirements. The validity of study C is low because of some fundamental limitations in the methods used to perform the study and/or the way methods are described in the report. It does not provide relevant information regarding the degree of compliance of rubber floor with legal minimum requirements. Therefore, results of study C cannot be used to provide evidence of the effect of rubber floor on welfare of sows. The findings of the three studies cannot be extrapolated to other pig categories. Experimental studies should cover the entire range of legal minimum floor requirements in the outcomes assessment and be done under different thermal scenarios. Variability at different experimental unit levels (i.e. individual animal, pen and farm level) should be adequately addressed in order to provide representative results.