Whether block-wall depressurization is the right answer in Hillsborough depends on what is actually under the floor.
The situations this follows from
- Radon entering high on the wall rather than at the floor
- An older block wall with an open top course
- A hollow concrete-block foundation wall
Why this comes up in Hillsborough
Here is what makes Hillsborough particular: the subdivisions and the mountain are not on the same supply. A well on the Sourland side draws from the diabase — the same rock that limits how far suction travels under a slab.
Hillsborough Township, Somerset County — the state's own numbers
32% of the 11,654 test results NJDEP holds for Hillsborough Township, Somerset County were at or above the 4.0 pCi/L action level — 3,785 of them. That puts it in Tier 1 — high potential.
Hillsborough is the large Somerset County township east of Hunterdon, running from the Sourland ridge down across the Millstone valley, and that shapes what a system here has to be designed around.
What access looks like here
Suburban lots with good access; the mountain properties are wooded and more constrained.
Construction permits go through Hillsborough Township, Somerset County, and installing radon mitigation for a fee anywhere in New Jersey requires NJDEP certification.
What the work involves
Hollow block walls are a network of interconnected voids running from the footing to the top course, and soil gas uses them as a chimney. Treating them means sealing the top course and drawing suction from inside the cavity, usually alongside a sub-slab system rather than instead of one.
Typical cost in Hunterdon County, NJ
$1,800 – $3,200 — typical range, not a quote. What your building needs can only be settled by a certified business that measures it on site.
Local experience matters here — the ground under Hillsborough does not behave like the other end of the county.
Certification, checked before referral
Installing radon mitigation for a fee in New Jersey requires NJDEP certification as a radon mitigation business, affiliated with a certified radon mitigation specialist (N.J.A.C. 7:28-27). We confirm that on the NJDEP register and record the date we checked. That is a check, not an endorsement — satisfy yourself before you hire.
System running and the reading hasn't moved?
Tell us what you've got — a number, an inspection report, or just a house you've never tested. We'll route it to certified crews near you.
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Related work in Hillsborough
Other work in Hillsborough
Same ground, different question.
Block-wall depressurization nearby
Neighbouring towns on the same ground.