What was your radon level before and after the mitigation system?

It depends on your house, because every basement starts at a different number. The EPA action level is 4.0 pCi/L, and a working active sub-slab system is built to pull the reading down below that. We do not promise a specific “after” number unless we put it in writing, and we do not run the after-test ourselves. You buy a fresh test kit, run it once the system has been on, and the kit tells you where you landed.

So the plain version. Your “before” is whatever your last test read. Your “after” should sit under 4.0, often well under it, once the fan has been running. The system does the work. The retest confirms it.

Why your starting number is so different from your neighbor’s

Radon comes up out of the ground and into the house through the slab, the floor wall joint, and any gaps around pipes. How much gets in depends on the soil under your slab, how tight the foundation is, and how the house pulls air. A house on the same street can read 2.0 while yours reads 11. That is normal. Soil and construction vary lot to lot.

That is also why we will not quote you an “after” number before we see the house. Branden, our radon guy (the crew calls him B-Radon), reads the slab, the crawl, and where the gas is getting in, then sizes the system to that. State radon cert RMS-113966, so this is done to code.

How the system actually drops the number

An active sub-slab system is a sealed pipe through the slab with a fan on it that runs around the clock. The fan pulls air and radon from under the floor and vents it up above the roofline before it can come inside. Slab gets sealed at the joints and penetrations so the suction works. The pressure under the slab flips, the gas goes up the pipe instead of into your basement, and the indoor reading falls.

If your house sits on a dirt or fieldstone crawl with no slab, we use a different method called sub-membrane depressurization. We lay a sealed membrane over the dirt and pull the radon from under that. We install both kinds, so the fix matches what you actually have.

What it costs and what moves the price

Radon mitigation runs $900 to $6,000, and most homes land around $1,950 to $2,250. The radon test fee is $50, credited toward the job if you move ahead. What moves the install price is the foundation type, how many suction points the slab needs, and the fan run for the pipe. A simple poured slab with one good suction point is the low end. A fieldstone foundation or a multi-level slab that needs more than one point sits higher, because there is more to seal and more pipe to run.

Here is the part nobody likes to hear, and we will say it anyway. A system that reads great on day one can drift if the fan ages or the seals fail. That is why the retest matters and why a working fan should never be off. The radon mitigation warranty is 10 years. There is no radon-level guarantee unless we put a number in writing, because your reading depends on soil and weather we do not control. If you want a guaranteed result number, ask us and we will talk about what we can stand behind in writing.

Do you even need one yet

If your last test read under 2.0, you are fine. No system needed. The EPA says to consider fixing between 2 and 4, and to fix at 4.0 and above. So test first. If you have never tested, that is step one, not the install. Most homeowners skip straight to “how much,” and the better question is “what does my house read right now.”

For the rest of the basement story, the radon system pairs with the rest of the work below. If you are also fighting water, see our basement waterproofing and the Forever Dry System. If the gas is coming up through a dirt crawl, that ties into crawl space services. Radon details live on the radon mitigation hub, and what we stand behind is spelled out on the 603 guarantee.

Outside reading worth your time: the EPA radon program for the 4.0 action level and the 2 to 4 guidance, and NH DHHS radon [verify] for state guidance.

We serve New Hampshire, Maine, and Massachusetts. Radon is high across a lot of New England granite country, so a high “before” number here is common, not a sign something is wrong with your house.

Call us at 603-610-1770 or book your free inspection and we will read your house, size the system to it, and give you a written quote within 24 hours.

Related questions

What radon level is dangerous? The EPA action level is 4.0 pCi/L. At 4.0 and above, fix it. Between 2 and 4, consider fixing. Under 2, you are fine. See the EPA radon program.

Do you retest after installing the system? No, the retest is the homeowner’s job. You run a fresh test kit once the fan has been on, and that reading is your “after.” We size and install the system to bring you under 4.0.

How much does radon mitigation cost? Radon mitigation runs $900 to $6,000, and most homes land around $1,950 to $2,250, and the test fee is $50, credited toward the job if you move ahead. Foundation type and the number of suction points move the price. We give a written quote within 24 hours of seeing the house. See radon mitigation.

Does a radon system come with a warranty? Yes, 10 years on the mitigation system. There is no guaranteed radon-level number unless we put it in writing, because your reading depends on soil and weather. Details on the 603 guarantee.