Radon and Finishing a Utah Basement

Why radon matters for basements

Radon is a naturally occurring radioactive gas that can seep into homes from the soil, and basements, being in contact with the ground, are often where levels are highest. Finishing a basement changes how much time people spend there: bedrooms, a family room, an office. That's why testing before you finish makes sense.

Utah homes above the action level

About one in three, according to Utah DEQ

EPA action level

4 pCi/L

Average Utah home

About 5.3 pCi/L, according to Utah DEQ

Test kit

About $11, according to Utah DEQ

Radon varies from house to house, even on the same street, so maps and averages only show tendencies. Only a test tells you your number. In Davis County, the health department offers free test kits during the winter months.

When and how to test

• Test before finishing, so mitigation can be planned into the layout.
• Test on the lowest level you'll use. Utah DEQ notes that if you start using a basement, you should retest on that level.
• Follow the kit's instructions on closed-house conditions and placement.
• Retest after finishing and after any mitigation to confirm results.

If the number is high

Utah DEQ advises contacting a certified radon mitigation professional when a home tests above 4 pCi/L. The common approach is sub-slab suction: a hole is bored through the basement slab, and a pipe and fan draw soil gas from under the slab and vent it outside. Costs depend on the house and the system, so get a quote from a certified professional.

Planning mitigation into the layout

A mitigation system is much easier to install neatly before the basement is finished:

• Suction pointOften near the mechanical room or in a storage area where the pipe can rise without crossing finished rooms.
• Pipe routeUp through a closet or chase, or out through a rim joist, planned before walls close.
• Fan powerAn outlet where the fan will be, usually outside or in the attic.
• SealingSealing slab cracks and penetrations before flooring goes down.

Short-term vs long-term tests

Short-term tests give a quick reading over a few days. Long-term tests average levels over a longer period and better reflect seasonal changes. A common approach is to start with a short-term test and follow up if results are near or above the action level. Follow the instructions that come with your test kit and Utah DEQ's guidance.

Talk to your contractor early

If you already know you'll mitigate, tell the contractor at the walkthrough. The suction point, pipe chase and fan power can be shown on the layout, and slab sealing can be scheduled before flooring. Waiting until after the basement is finished usually means a pipe running through a finished room or a less tidy route.

What Utah code says

Radon-resistant construction is voluntary in Utah. The state's code amendments say that when passive radon controls are voluntarily installed, they must comply with IRC Appendix F. Your city won't require a test for a basement finish, but nothing stops you from planning for it.

How it fits the walkthrough

If you've tested, share the result at the free walkthrough. If mitigation is needed, the layout sketch can reserve a route for it, and the scope can note it, even if the system itself is installed by a separate specialist.

Common questions