The rats we have had in our house avoided snap traps (no matter what the bait); they were too wary of anything new.
I started with repointing the stacked stoned foundation. I filled every gap between the floors and plumbing, electrical wiring, etc with steel wool. If the gap was large I covered the gap with metal flashing or wire window screen (not the newer plastic stuff). Basement windows are covered on the outside with hardware cloth (1/4"x1/4" wire mesh); if I could I had it overhanging the wooden frames out to the stone foundation so they didn't have access to wood.
We then put out second generation rat poison in the basement under a milk crate. I also dropped it down inside the walls from the attic (we could hear them in the walls). We monitor the dirt floor in the basement for excavation of holes to let us know if we have new rats. Every year we get one or two new rats in the house; I'm not sure how they are getting in.
Until you wake-up hearing rat fur rubbing in the walls behind your head board at night, hearing them chewing on the framing near your bedroom window at night, or the framing of the stairs you won't know how willing you are to use poison.