Published October 1, 2026

Selling a House With Radon in NH (2026)

Written by Aaron Phinney

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Quick answer: You can sell a house with radon in New Hampshire. State law (RSA 477:4-a) requires you to give buyers a general radon notice before the contract is signed, but it does not require you to test or fix. If a test comes back at or above 4 pCi/L, a mitigation system usually runs about $1,000 to $2,500 and installs in a day, so it is a manageable fix, not a deal-breaker.

Selling a house with radon in New Hampshire sounds alarming until you look at the numbers. The state health department reports that 37% of tested New Hampshire homes came back at 4.0 pCi/L or higher, so an elevated reading is common here, not a sign that something is wrong with your house. What hurts sellers is not the radon itself. It is finding out during the buyer's inspection window, with the clock running and a nervous buyer asking for a big credit. This guide explains what you must tell buyers, whether to test before listing, what mitigation costs, and how the negotiation usually goes. It is general information, not legal advice, so check your situation with your attorney.

Is Radon Common in New Hampshire Homes?

Yes. According to the New Hampshire DHHS radon data brief, 37% of homes tested between 2007 and 2021 (32,747 samples) measured 4.0 pCi/L or higher. The average indoor reading was about 5.9 pCi/L, against a national average of roughly 1.3. In Rockingham County, where many of our southern New Hampshire clients live, half of tested homes were at 7.9 pCi/L or higher. The brief also notes that readings above 100 pCi/L have turned up in every county. The takeaway for a seller: the buyer's inspector will almost certainly recommend a radon test, so assume it is coming and plan for it. For the buyer's view, see our radon testing guide for New Hampshire buyers.

Do You Have to Disclose Radon When Selling a House in NH?

New Hampshire handles radon through a notice. Under RSA 477:4-a, the seller or seller's agent must notify the buyer, before the purchase and sale contract is signed, that radon may be found in some areas of the state, that it can enter a building through the ground or through water from a deep well, and that testing and removal equipment exist. The buyer acknowledges receipt by signing a copy. In practice this notice is built into the standard disclosure paperwork, which we walk through in our guide to seller disclosure requirements in New Hampshire.

Two things the statute does not do: it does not require you to test, and it does not set a legal pass/fail number. The federal action level of 4 pCi/L is the benchmark everyone uses, but it is guidance. What it does not mean is that you can ignore results you already have. If you tested last year and got a high reading, or you installed a system, talk to your attorney about how to handle direct questions and the disclosure form, because a misleading answer on a known issue is the kind of thing that turns into a dispute after closing.

Should You Test for Radon Before Listing Your House?

For most sellers, yes. When you are selling a house with radon in New Hampshire, or might be, a short-term test is inexpensive, and it converts an unknown into a known number while you still control the timeline. Most real estate radon tests run about 48 hours, and a professional certified in radon testing is the standard for a test the buyer will accept. Why testing first tends to pay off:

No surprise during the inspection window. If the buyer's test is the first anyone has seen, any high result lands in the middle of a negotiation.
Time to get quotes. You can compare two mitigation contractors instead of accepting whatever number the buyer's side brings back.
A marketing point. "Radon mitigation system installed" with a post-fix test reads as a maintained house, not a problem house.

Fall is a good time to do it. Houses are closed up as the heating season starts, which gives a more representative reading than an open-window test in July. Test in the lowest livable level of the house, keep windows and exterior doors closed as the tester instructs, and keep the report. It also pairs well with a broader pre-listing inspection if you are weighing one.

How Much Does Radon Mitigation Cost in New Hampshire?

A typical New Hampshire single-family mitigation, usually a sub-slab depressurization system, installs in a single day and commonly costs about $1,000 to $2,500, according to a New Hampshire radon contractor's seller guidance. Installation takes roughly 4 to 8 hours, and the whole sequence from assessment through the post-installation test often fits in 10 to 14 days. Houses with crawlspaces, complicated foundations, or very high readings can cost more, so treat these as typical ranges and get written quotes. Radon is among the cheaper problems a buyer's inspection can uncover. You can see where a mitigation credit fits next to commission and closing items in our breakdown of what it costs to sell a house in New Hampshire.

What Happens If the Buyer's Radon Test Comes Back High?

This is the part sellers worry about, and it is usually less dramatic than expected. Selling a house with radon in New Hampshire usually comes down to paperwork and a quote. If the buyer's test is at or above 4 pCi/L, the common outcomes are:

The seller installs a system before closing and provides the post-installation test result.
The seller gives a closing credit and the buyer handles installation after purchase.
A price adjustment that reflects the quote.
The buyer accepts the result and moves ahead, which happens more often than sellers expect when the reading is modest.

Who pays is negotiable. What keeps it small is documentation: a licensed contractor's quote, a clear test report, and a retest after the work showing the number came down. Buyers who see a number and a plan tend to ask for the cost of the fix. Buyers who see only a number tend to ask for a lot more. If the house needs several repairs, our guide on what to fix before selling your NH home helps you rank what is worth doing first, and if you would rather not repair anything, read how selling a house as-is in New Hampshire works.

What If Your Radon Is in the Water, Not Just the Air?

Radon can also enter a home through water from a deep drilled well, which is why the state's notice mentions it. Water testing is done by an accredited laboratory, separately from an air test, and treatment equipment exists for water as well as air. If your home is on a private well, add a water radon test to your pre-listing checklist so the buyer's well-water testing holds no surprises.

Frequently Asked Questions

Can you sell a house with high radon in New Hampshire?

Yes. High radon is common here and is routinely fixed with a mitigation system. You can install one before closing, credit the buyer, adjust the price, or sell as-is, as long as you complete the required notice and answer disclosure questions accurately.

Is radon testing required to sell a house in NH?

No statute requires the seller to test. Buyers usually order their own test during the inspection period, which is why many sellers test first to avoid surprises and control timing.

What radon level is too high for a home sale?

The common benchmark is 4.0 pCi/L, the federal action level. Results at or above it normally lead to a mitigation recommendation, although the level is guidance, not a legal pass/fail number for a sale.

Who pays for radon mitigation when selling a house in NH?

It is negotiated. Either the seller installs a system before closing, or the buyer receives a closing credit and installs it after purchase. Typical installation costs about $1,000 to $2,500.

How long does radon mitigation take?

A standard system installs in 4 to 8 hours, and the full process from assessment to a post-installation retest often takes 10 to 14 days.

Do I need to retest after installing a radon system?

Yes. A post-installation test confirms the number is below the action level and gives the next buyer written proof the system works.

Selling a house with radon in New Hampshire and wondering how it will affect your price or timeline? Request a free home valuation from The Phinney Team and we will help you decide whether to test first, how to handle quotes, and how to price with the result in mind. You can learn more about working with us at teamphinney.com, and find state homeowner information at NHDES Radon.