My grandparents have enlisted my help installing a laminate floor in their living room. I’ve put it in before, but it was installed on plywood, and they have a slab house. Will they need a vapor barrier between the floor and concrete, and if so any recommendations. Also when installing the transition pieces what would be the best way to fasten them down. On mine I just screwed them into the plywood underneath, no experience with concrete. There are two doorways that will need them, one leading outside and one leading into the kitchen. Any help or insight is appreciated.