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Home Buyers - Know What to Ask For
Basic Radon-Resistant New Construction Techniques for Your Home
All of the techniques and materials described below are commonly used in home construction. No special skills or materials are required when adding radon-resistant features as a new home is being built.
While the techniques may vary for different house foundations and building site requirements, the five basic features that all builders should include to prevent radon from entering your home are:
- Gravel: A 4-inch layer of clean, coarse gravel below the “slab,” also called the foundation. This layer of gravel allows the soil gases—including radon—that occur naturally in the soil to move freely underneath the house. Builders call this the “air flow layer or gas permeable layer” because the loose gravel allows the gases to circulate.
NOTE: In some regions of the country, gravel may be too expensive or unnecessary. Alternatives are allowed, such as a perforated pipe or a collection mat. (See Building Radon Out (PDF, 84 pp, 5.5MB, about PDF), pp. 35-40 for more information.)
- Plastic Sheeting or Vapor Retarder: Heavy duty plastic sheeting (6 mil. polyethylene) or a vapor retarder is placed on top of the gravel to prevent the soil gases from entering the house. The sheeting also keeps the concrete from clogging the gravel layer when the slab is poured.
- A Vent Pipe: A 3-inch or 4-inch solid PVC Schedule 40 pipe, like the ones commonly used for plumbing, runs vertically from the gravel layer (stubbed up when the slab is poured) through the house’s conditioned space and roof to safely vent radon and other soil gases outside above the house. (Although serving a different purpose, this vent pipe is similar to the drain waste vent—DWV—installed by the plumber.) This pipe should be labeled "Radon System." Your plumber or a certified radon professional can do this. Visit NEHA/NRPP
or NRSB
to find out how to find a qualified radon service provider in your area.
- Sealing and Caulking: All openings, cracks, and crevices in the concrete foundation floor (including the slab perimeter crack) and walls are sealed with polyurethane caulk to prevent radon and other soil gases from entering the home.
- Junction Box: Install an electrical junction box (outlet) in the attic for use with a vent fan, should, after testing for radon, a more robust system be needed.
All homes should be tested for radon. Find a qualified radon service provider near you.
Many builders routinely include these features in some of their homes. They often will provide a checklist of included features (available here as a PDF file (PDF, 1 page, 381KB, About PDF)). As a new home buyer, you should ask the builder about these features. If not provided for, ask your builder to include them in your new home. If a home is tested after buyers move in and an elevated level of radon is discovered, the owners’ cost of fixing the problem can be much more.