Plenty of Sandy houses are not one thing underneath. A split-level, or an addition built a decade after the original, can leave you with a slab under part of the house…
Plenty of Sandy houses are not one thing underneath. A split-level, or an addition built a decade after the original, can leave you with a slab under part of the house and a crawl space under the rest, sometimes separated by a stem wall you cannot see from either side. Radon comes up out of the ground, so both areas sit against the same source, but they behave differently. A slab is a barrier with joints and penetrations through it. A crawl space is often open soil with a floor above it. One approach to mitigation does not automatically serve both.
That is why the diagnostic visit matters more on a mixed-foundation house than on a simple one. A contractor wants to know where the slab ends, whether the crawl space is vented or sealed, what the ground surface down there looks like, and whether air moves freely between the two zones or is blocked by footings. Those answers decide how many suction points the design needs and where they go. It is ordinary work rather than exotic work, but it is the difference between a system that holds the whole footprint and one that covers half the house.
Under a slab, the standard fix is sub-slab depressurization: a pipe through the concrete, a fan pulling soil gas from the gravel or soil below, and a discharge above the roofline. A crawl space follows the same principle with a different surface. A membrane is laid over the exposed soil and sealed at the perimeter and around piers, and suction is drawn from beneath it, so the membrane does the job the slab does elsewhere in the house. The two zones can often share a single fan and one vent run, or they may need separate suction points tied together into it.
Getting that right is a design question rather than a product question. If the crawl space and the slab area are effectively isolated from one another, treating one alone can leave the other untouched, and the finished test will show it. This is another reason re-testing after installation is not a formality. The post-installation measurement is the only evidence that the design reached both parts of the house. If it did not, the remedy is usually an added suction point rather than starting the whole job over from the beginning.
Placement matters in a house with several floor levels. Testing is generally done in the lowest lived-in level of the home, following the instructions that come with the kit or the protocol a measurement professional works to. A crawl space itself is not a living area and is not usually where the number that matters comes from. If your house has a finished lower level over a slab and a crawl space under a rear addition, say so when you order a test or book a measurement, because it can affect where the detector goes and how the result should be read.
A short-term test gives a quick reading, while a long-term test tracks levels through changing weather and seasons and so better reflects a year-round average for the house. Current thresholds are not ours to state: the EPA publishes an action level and the Utah Department of Environmental Quality publishes Utah-specific guidance and radon maps, and those are the places to confirm the figures before you draw conclusions from a number. When you are ready to talk with a contractor who has designed systems for mixed foundations elsewhere in Salt Lake County, call 801-644-9000 and we will make the introduction.
It depends on how the two areas connect and where the detector sat. A reading taken over the slab may not describe the part of the house above the crawl space, particularly when the zones are separated by a stem wall. A contractor looks at both during the site visit, and additional testing can clarify it. The post-installation test then confirms whether the finished design covered the entire footprint.
Laid loose, no. The membrane matters because suction is drawn from beneath it, which requires it to be sealed at the perimeter, at piers, and along seams so the fan can maintain a pressure difference. Without that, soil gas simply moves around the edges. In a radon design the membrane is a working surface for the system rather than a standalone barrier, and the test afterward shows whether it is doing its job.
Often yes. Suction points from each zone can be tied into a shared pipe run with one fan and a single discharge above the roofline, provided the fan can hold enough suction across both. Whether that works depends on the material under the slab, the size of the crawl space, and how the areas connect. A contractor determines it during diagnostics rather than guessing from outside the house.
Everything begins with a measurement. A contractor places a short-term device for a quick reading or a long-term device for a closer look at your yearly average, then hands you a number you can make a decision from.
Learn more →When a reading sits at or above the action level the EPA publishes, the standard remedy is sub-slab depressurization: a sealed pipe and a fan that draw soil gas from beneath the slab and vent it above the roofline.
Learn more →A sale runs on its own clock. Radon tests during a transaction carry timing rules and closed-house requirements, and it saves friction to settle early who orders the test and who deals with the result.
Learn more →Fans do not run forever, and the little monitor on the pipe is easy to stop noticing. Service means checking that gauge, confirming the fan still pulls, replacing it at end of life, and re-testing to prove the system still works.
Learn more →During a build, the pipe can be run before the drywall closes the walls. A passive rough-in is far simpler than routing a system through a finished house, and adding a fan later is a small job.
Learn more →Test first, then decide. There is no fee to be matched.
Call 801-644-9000County, foundation type, and whether a deadline is involved is enough to start.