Radon pipe under garage

This is a homeowner forum question rather than a news story, so there's no expert answer to report yet. A homeowner building a new two-story house asked about radon protection: part of the second floor sits above an attached garage, and that garage has its own concrete slab poured directly on the ground, separate from the basement under the rest of the house. The plan is to run a radon mitigation loop — perforated pipe under the slab that vents soil gas up and out through the roof — beneath the basement. The homeowner's question is whether the garage slab needs its own separate loop too, since living space sits above it.

No replies had been posted when this was captured, so there's no verdict to pass along. But the underlying concern is worth knowing if you're building or renovating a house with a similar layout: radon gas comes up through soil under any slab-on-grade area, not just basements, and if occupied rooms sit above a garage, gas that seeps into the slab could theoretically make its way into that living space. Homeowners in this situation may want to ask their builder or a radon specialist whether a single loop under the basement is enough, or whether the garage slab needs its own independent line, especially given radon levels vary a lot by location and soil type.