One of the most common things we hear on the phone is some version of "but the house is only four years old." A buyer under contract on a 2021 build in Ooltewah or Apison gets a radon result of 7 or 8 pCi/L back from the inspector and assumes something is wrong with the test. Nothing is wrong with the test. Radon has nothing to do with how old a house is, and a few things about modern construction actually make it worse.
Radon is a gas produced by uranium breaking down in rock and soil. The limestone and shale under Hamilton County produce plenty of it, which is why the whole area sits in a zone where elevated readings are common. The gas moves up through the soil and into any building sitting on top of it, through cracks, joints, sump pits, and the pores in concrete itself. A house built last year sits on the same ground as the 1950s ranch next door. Read more about local readings on our radon levels page.
Tighter envelopes. Modern homes are built to hold conditioned air. Spray foam, house wrap, sealed windows and tight ductwork all mean less air exchange with the outside, so whatever radon enters stays in the house longer instead of leaking out.
Walkout and daylight basements. New subdivisions on Chattanooga's hillsides are full of them. A walkout basement is cut into a slope, which puts a large area of below grade wall and floor in direct contact with disturbed soil and rock. Bigger contact area, more entry points.
Finished lower levels. When the basement is a family room and a guest suite, people spend hours a day at the level closest to the source, which is exactly why the test is placed there.
Disturbed ground. Grading a lot loosens the soil and opens up pathways that were compacted for centuries. It can take years for that to settle.
Many builders in Hamilton County now install a passive radon rough-in: a pipe running from the gravel under the slab up through the house and out the roof, with no fan on it. Look for a capped pipe in a mechanical room or utility closet, sometimes labeled "radon." If your new home has one, activating it means adding a fan and a monitor, which is a short visit and typically $500 to $900 rather than the $1,400 to $1,800 a full system costs when the pipe has to be routed from scratch. See our mitigation cost guide for the details.
If the house does not have a rough-in, a standard sub-slab system still works exactly the same way it does in an older home. The concrete is newer and usually in better shape, which if anything makes the seal easier.
A high reading on a new house is a negotiating item, not a reason to walk. Sellers and builders routinely cover mitigation, and a system with a written guarantee to bring the level under 4.0 pCi/L closes the issue for the lender and for you. Our real estate radon guide walks through the timing, and we can install inside a standard inspection window.
Call (423) 529-4385 and tell us the year built, whether there is a basement or crawl space, and whether you can find a radon stub pipe. We will give you a straight price on the phone.
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