Basements and crawlspaces are where radon problems live. These below-grade spaces sit closest to the soil source, and in Calgary they are also where many families spend real time — in finished basement bedrooms, family rooms, and home offices. Mitigating radon in these spaces requires the right approach for the foundation you have. Here is how it works for both concrete basements and dirt crawlspaces.
Radon enters from the soil, so the lower you go, the closer you are to the source. A basement floor sits directly on the gravel and soil where radon is generated, and any crack, joint, or opening becomes a pathway. In a dirt crawlspace, there may be no barrier at all between the soil and your indoor air. Add Calgary's airtight winter homes and furnace-driven negative pressure, and below-grade spaces become radon collection points.
For a poured concrete slab, the proven method is sub-slab depressurization. The installer cores through the slab, excavates a small suction pit in the gravel beneath, and connects a sealed pipe to a radon fan. The fan creates lower pressure under the slab than in your living space, so radon is captured below the floor and vented outside above the roofline rather than seeping up into the basement.
Major foundation cracks, the gap around a sump pit, floor drains, and openings where pipes pass through are sealed to make the system as efficient as possible. Sealing alone is not a fix, but paired with active depressurization it helps achieve the lowest possible levels.
A developed basement adds a wrinkle: the slab and entry points may be hidden behind drywall, flooring, and ceilings. An experienced contractor plans the suction point and pipe routing to minimize disruption — often using a utility room, mechanical closet, or unfinished corner. With careful planning, even a fully finished Calgary basement can be mitigated cleanly.
Dirt-floor crawlspaces are common in older Calgary homes and additions, and they can be significant radon sources because bare soil offers no resistance to gas entry.
The solution is sub-membrane depressurization. A durable polyethylene membrane is laid over the entire crawlspace floor, sealed at the seams and around the perimeter and any piers. A perforated pipe runs beneath the membrane, connected to a radon fan. The fan draws radon from under the sealed barrier and vents it outdoors, while the membrane prevents soil gas from entering the crawlspace and migrating into the home above.
Beyond radon, a sealed crawlspace membrane reduces soil moisture and humidity, which helps protect against mould and rot and improves overall air quality in the home. It is a worthwhile upgrade on multiple fronts.
Many Calgary homes combine a basement with a crawlspace, or have an addition on a separate slab. These mixed foundations may require more than one suction point or a combination of sub-slab and sub-membrane systems tied together. This is exactly the kind of situation where a careful professional assessment pays off — a one-size-fits-all approach will not reliably bring levels down.
Whether your home has a slab, a crawlspace, or both, the work is only done when it is proven. A post-mitigation radon test confirms the new, lower level. Onyx Radon includes verification testing with every installation, so you receive documented evidence that your basement or crawlspace is below the 200 Bq/m³ guideline.
The right mitigation method depends on what is under your home. Concrete basements call for sub-slab depressurization; dirt crawlspaces call for a sealed membrane and sub-membrane depressurization. With a C-NRPP certified design tailored to your foundation, Onyx Radon delivers rock-solid protection in the very spaces where radon is most concentrated.
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