Radon Rough-Ins: A Quiet Change in the 2020 Code Series

Radon is a naturally occurring radioactive gas that can seep into a building from the soil beneath it, and it's the second-leading cause of lung cancer after smoking. The 2020 series of national model codes strengthened provisions around radon, including sub-slab depressurization rough-ins — a sealed pipe run from beneath the foundation up through the building — that make it far cheaper to add active mitigation later if a test comes back high.

The rough-in itself doesn't require running a fan; it just leaves the infrastructure in place. That distinction matters, because retrofitting a full mitigation system into a finished basement after the fact is a much bigger job than capping off a pipe that was already run during construction. Radon levels vary significantly by region and even by lot, so testing after move-in is still worth doing regardless of what the rough-in requirement was at build time.