Sub-Slab Depressurization Explained for York County Homes

Most radon mitigation systems follow the same basic principle: intercept the gas below the home and vent it outside before it has a chance to build up indoors. Sub-slab depressurization is the standard approach for homes with a concrete slab or basement floor, and it is what most York County homes end up with.

Radon in York County homes typically enters through the foundation, cracks in the slab, sump pits, or crawlspaces. Rather than trying to seal every possible entry point, a sub-slab system creates a continuous low-pressure zone beneath the floor that draws soil gas into a pipe instead of letting it seep upward.

A sub-slab depressurization system has a few simple, durable parts that work together:

• A suction point, created by coring a hole through the slab and sealing a PVC pipe into it.
• PVC piping that runs from the suction point up through the home, usually routed through a closet, garage, or along an exterior wall.
• An inline fan that creates continuous negative pressure, pulling soil gas from under the slab into the pipe.
• An exhaust above the roofline, positioned away from windows and openings so the vented gas disperses safely outdoors.
• A system label and a manometer gauge so anyone in the home can see the system is running and know what it is.

Homes with more than one foundation section, or a larger footprint, sometimes need more than one suction point to pull air evenly from under the entire slab. A single point can leave dead zones where radon still collects, which is one reason a low bid sometimes means a single suction point where your home actually needs two.

This is exactly why a certified mitigator evaluates your foundation first. A proper design matches the suction layout to how air actually moves beneath your specific home, not a one-size-fits-all package.

If part or all of your York County home sits over a crawlspace instead of a slab, the system usually pairs a heavy-duty vapor membrane laid across the crawlspace floor with a suction point that draws air from beneath that membrane. The same fan-and-exhaust logic applies, it is just adapted to a dirt or gravel floor instead of concrete.

Homes with mixed foundations, a basement plus a crawlspace, may need a combined approach with both a sub-slab point and a membrane suction point tied into the same fan.

Sealing visible cracks, gaps around pipes, and sump pit covers is a reasonable support step, and a good contractor will usually do some of it as part of the job. On its own, though, sealing is not a mitigation system. It does not create the negative pressure needed to actually pull radon out from under the home, so it should never be sold to you as a standalone fix.

A properly installed system has a few clear signs: the fan runs continuously and quietly, the system is labeled so anyone in the home knows what it is, and a post-installation retest shows a meaningfully lower number than what you started with. If any of those three things are missing, the job is not finished.