Steel fibre reinforced self-stressing concrete (SFRSSC) has been developing steadily over the last decades with applications of the material now including ground and pile supported slabs as well as raft foundations. Such building elements commonly come into contact with groundwater and are therefore typically covered on their exterior surface by a waterproofing membrane system in an attempt to prevent water seepage into the structure. The final performance of a waterproofing membrane system is heavily influenced by the quality, skill, and attention to detail both in the installation of the membrane and during subsequent works carried out (e.g., reinforcement placement, concrete pouring, etc.) over top of the membrane. Concrete slabs and foundations constructed using SFRSSC, which is typically less prone to cracking than ordinary concrete, may potentially have improved resistance to water ingress than ordinary concrete. In this paper, water penetration testing per EN 12390-8 and mercury intrusion porosimetry testing are completed on various SFRSSC mixtures and compared to reference concrete mixtures to assess changes in the material pore size distribution and its ability to resist water penetration. The presented test results indicate that SFRSSC can have a more refined pore network with improved resistance to water penetration compared to reference concrete mixes with the same water-to-cement ratio. As discussed in the paper, the SFRSSC additional characteristic of reduced shrinkage (and subsequent reduced potential for cracking) indicates that the material may be able to provide improved watertightness, with a potential to reduce demands for external waterproofing membranes under certain circumstances. © 2020 Latvia University of Life Sciences and Technologies. All rights reserved.