Why are rain gutters sometimes used for radon mitigation systems?

Rain gutters are not part of the radon system itself. They come up because keeping roof water away from your foundation keeps the soil under your slab drier, and a radon fan pulls a cleaner, steadier vacuum through dry soil than through wet, saturated ground. So gutters and downspouts support the radon fix. They do not replace it.

A radon mitigation system is called active soil depressurization. A pipe goes through the slab, a fan runs on that pipe, and it creates suction under your foundation. That suction pulls radon out from beneath the house and vents it above the roofline before it gets into the air you breathe. The EPA calls this the standard fix, and it is the one we install in most homes. (Source: EPA.)

Here is where water enters the story. The fan pulls air through the soil and gravel under your slab. Dry, loose soil lets air move easily. Soaked soil holds water in the gaps the air would travel through, so the fan fights to pull a vacuum. Around a New Hampshire foundation, the ground near the wall is disturbed backfill. That is the looser fill put back when the house was built. It drains slowly and holds water, so it is the soil most likely to stay wet after a storm.

That is the connection. Working gutters and downspouts carry roof water out past that backfill instead of dumping it at the foundation. Drier soil under the slab, a fan that pulls cleaner, a radon system that runs right. Building-science groups like the U.S. Department of Energy’s Building America program treat roof-water control as a basic part of keeping foundation soil dry. (Source: DOE Building America.)

There is a second reason. The same openings that let radon in also let water in. Cracks in the slab, the floor wall joint where the slab meets the wall, gaps around pipes, an open sump pit. A radon job seals those so the fan is not wasting suction on room air pulled through a crack. If water keeps pouring in at the foundation, it works against that sealing. So we look at the roof water first.

You do not need a fancy gutter system to help a radon fan. You need gutters that move water away from the house. Clogged gutters, a downspout ending at the wall, a missing extension. Those keep the backfill wet.

What this means for your home

If your home tested high for radon, the fix is the radon system, not the gutters. Get active soil depressurization installed by a certified contractor. We are state radon certified (cert RMS-113966) and install these in-house across New Hampshire, Maine, and Massachusetts.

While you are planning it, look at your roof water. Walk the house in a hard rain if you can. Water pooling at the foundation, downspouts dumping at the wall, an overflowing gutter. Those keep the soil under your slab wet and make the fan work harder.

If your basement also takes on water, that is a bigger conversation. The cracks and the sump that let radon in are the same ones that let water in, so it often makes sense to look at radon and waterproofing together. Our Forever Dry System handles the water side, and it is for basements only. For the gas, see our radon mitigation page.

A radon mitigation system in New Hampshire costs $900 to $6,000, and most homes land around $1,950 to $2,250, depending on home size, foundation type, and how many entry points have to be sealed. A radon test runs $50, credited toward the job if you move ahead. Our mitigation systems carry a 10-year warranty on system integrity and components. We do not promise a specific post-mitigation radon number unless we put it in writing, because the final level depends on your house.

One thing we will tell you plainly. Do not let anyone sell you a radon system as a waterproofing fix, and do not let anyone sell you gutters as a radon fix. They are different jobs. Gutters help the radon system run better and keep your basement dry. They do not lower a radon reading on their own. If your number is high, you need the fan and the sealing.

The EPA action level is 4.0 pCi/L. Test at or above that and they recommend you fix it, and they suggest you consider a fix between 2 and 4 too. (Source: EPA.) Your state radon office is a good neutral starting point as well. (Source: NH DHHS.)

Ready to look at it?

We will come out, look at your basement, your radon situation, and your roof water, and tell you what you actually need. The inspection and estimate are free, and we get you a quote within 24 hours.

Call us at 603-610-1770, or book your free inspection. If you are in Exeter or the next town over, we have probably worked on your street.

Related questions

Will fixing my gutters lower my radon level?

Not on its own. Gutters keep the soil under your slab drier, which helps a radon fan pull a cleaner vacuum, but they do not pull radon out of the ground. If your home tests at or above 4.0 pCi/L, you need an active soil depressurization system. Gutters help it run better.

Does a radon system also keep my basement dry?

No. A radon system moves gas, not water. To stop water you need drainage and a sump, which is our Forever Dry System, a basement-only fix. Some homes need both, and the sealing overlaps, so it is worth looking at them together.

How much does radon mitigation cost in New Hampshire?

A radon mitigation system runs $900 to $6,000, and most homes land around $1,950 to $2,250, depending on home size, foundation type, and how many entry points have to be sealed. A simple slab sits on the low end. An older fieldstone basement runs toward the high end. A radon test is $50, credited toward the job if you move ahead, and crack repair on a foundation crack starts at $1,000 to $3,000. We give you a quote within 24 hours.

Related answers: More radon answers · How can airflow and HVAC systems affect radon levels throughout a house? · Will portable home air cleaners reduce radon? · If a basement’s concrete cracks, will radon get into the air inside the house?