Guide

Radon-Resistant New Construction in York County, PA

Updated October 20, 2026

Radon comes from uranium decay in the soil and bedrock under the lot, not from the age of the house, so a new home on York County soil faces the same source as the farmhouse next door. PA DEP puts the average residential radon level in Pennsylvania at 7 to 8 pCi/L, well above EPA's 4 pCi/L action level, and it points out that there is no reliable way to test the ground before building. A passive system built in during construction is a head start, not immunity. This page covers what goes in, what it costs, what the law does and does not require, and what to check before the slab is poured. For the retrofit side, see radon mitigation in York, PA for existing homes.

Does Pennsylvania require radon-resistant new construction?

No, not statewide. PA DEP's page on radon-resistant new construction states that "the statewide building code does not require radon-resistant new construction. However, local municipalities may have adopted this portion of the building code." The model-code text, Appendix F of the International Residential Code, says its provisions are not mandatory unless the adopting ordinance references them. Several states and many local governments elsewhere do adopt it. EPA recommends radon-resistant features in every Zone 1 county, and York County is one.

In practice, whether your new home has a radon rough-in depends on your builder and your township. Some York County builders include it as standard and some do not. If it is not in your plans, ask for it before the slab is poured, because it is cheapest at that moment. Whether your township has adopted Appendix F is a question for its code enforcement office. For the county picture, see the EPA radon zone map explained and York County radon levels.

The five parts of a passive radon system

EPA's radon-resistant construction guidance lists five basic features for a house on a slab or basement foundation:

1. Gravel layer. A 4-inch layer of clean, coarse gravel under the slab lets soil gas move freely to a collection point. EPA allows alternatives such as a perforated pipe or a collection mat where gravel is impractical
2. Plastic sheeting. Heavy-duty polyethylene sheeting over the gravel, with overlapping seams, acts as the vapor retarder and keeps soil gas from rising through the slab
3. Sealing. Openings, cracks, joints and utility penetrations in the slab and foundation walls are sealed with polyurethane caulk, which is far easier at the time of the pour than after the home is finished
4. Vent pipe. A 3-inch or 4-inch gas-tight pipe runs from the gravel layer up through the house and out above the roof, labeled so nobody caps it or ties other plumbing into it
5. Junction box. An electrical box is wired in the attic or at the fan location, so a fan can be added without opening walls

The gravel and sheeting vanish under concrete on pour day. If you are building, ask your builder for dated photos of both before the pour, and ask to see the pipe stub rising out of the gravel. After the concrete cures, that is the last time anyone can verify them. PA DEP cautions that the work is straightforward but has many pitfalls, and that builders doing it should read the available material first.

Passive versus active, and how a passive system gets a fan

A passive system relies on the natural upward flow of warm air (the stack effect) to draw soil gas up the vent pipe. EPA's Consumer's Guide to Radon Reduction rates passive sub-slab suction at about 30 to 70 percent reduction, which is useful but less than the 50 to 99 percent of an active system. Adding an in-line fan to the same pipe turns it into the active system, which is why the rough-in matters so much. Read more in our passive vs. active systems guide.

Activation is typically quick: a certified mitigator checks the pipe, installs the fan on the attic or exterior section, seals and tests it, and installs a manometer so you can see it working. After activation, Pennsylvania rules require a post-mitigation test between 24 hours and 30 days later (25 Pa. Code § 240.310). Because the hard part, running the pipe and penetrating the roof, is already done, this is typically the cheapest mitigation retrofit there is.

What it costs: build it in or add it later

EPA's builder figures are from its 2001 guide and builders now report higher material and labor costs. PA DEP says only that installing the system during construction should cost less than installing it afterward.

A passive rough-in also keeps the pipe inside the house. DEP notes that if radon is not addressed during construction and the test comes back above 4 pCi/L, an outside radon system may be required. Most buyers prefer the interior route.

Why a new home should still be tested

Both agencies are direct on this. EPA writes that even if built radon-resistant, every new home should be tested after occupancy. A passive system lowers risk, and in many homes it brings the number under 4 pCi/L. It does not guarantee that outcome, especially in a county where the soil source is strong. Newer homes also tend to be tight and well insulated, so there is less air exchange to dilute whatever does enter. Test within the first few weeks, using a short-term test, and consider a long-term test if the result lands close to 4. Our guide to short-term vs. long-term radon tests explains which to use.

What to ask your builder

• Is a radon rough-in in the plans and the contract, and which of the five parts does it include?
• Will you send dated photos of the gravel layer, the sheeting and the pipe stub before the pour?
• Is the vent pipe continuous to above the roof, labeled, and kept clear of other pipes and framing?
• Is there an outlet or junction box at the fan location?
• Who will test the house after the final inspection, and will you hand over the result?

Our contractor guide explains how to confirm DEP certification before anyone touches the system after move-in.

Common questions

Is radon-resistant construction required in Pennsylvania?

Not statewide. PA DEP states that the statewide building code does not require radon-resistant new construction, although local municipalities may have adopted that portion of the code. The relevant model-code section, Appendix F of the International Residential Code, is optional unless a jurisdiction adopts it by ordinance. Ask your township code office and your builder what applies to your lot.

Does a passive radon system mean my new home is safe?

No. EPA lists passive sub-slab suction at about 30 to 70 percent reduction, while an active system with a fan reaches 50 to 99 percent. Both EPA and PA DEP say every new home should be tested after move-in, even if it was built radon-resistant.

How much does it cost to add a fan to a passive radon system?

Our cost guide lists a fan added to an existing rough-in at about $350 to $1,200, with $500 typical. Cost depends on how the pipe is routed and where the attic or garage fan location sits. The EPA builder guide states that retrofitting a home with no rough-in typically costs $800 to $2,500, in older dollars.

Do I need a certified mitigator to build the passive system?

PA DEP says hiring a Pennsylvania-certified mitigator during construction is not required but would be beneficial. Anyone doing radon work after the home is occupied does need DEP certification, which includes activating the system with a fan.

When should I test a new home for radon?

Soon after you move in. PA DEP recommends testing shortly after occupancy to decide whether the passive system needs a fan, and EPA recommends the same. Use a short-term test first. See radon testing for how to do it properly.