I currently have a cement slab used for a mini full court basketball. My father and I poured the cement ourselves, so it's not exactly perfect. It has small portions of it that when it rains, creates a small puddle. Will this be an issue if I install the rubber flooring on top of the current cement slab?
If water were to seep onto the underlayment, the water would sit on top of the underlayment or get into the pores and evaporate. The water will not destroy or affect the underlay in any way. This should not be an issue.