Foundation-specific
Crawl Space Radon Mitigation
A crawl space with an earth floor has no slab to draw from, so the system has to create its own barrier first. That difference — building the surface the system works against — is what separates crawl space projects from basement projects in labor, materials and price.
Why exposed soil changes the problem
In a basement, the concrete slab already separates the soil from the interior; mitigation simply exploits the space beneath it. In a crawl space with bare earth, soil gas has an open, continuous surface to enter through, and the crawl space air often communicates with the living space above through the floor system.
The system therefore starts with a sealed membrane laid over the soil, which becomes the barrier the fan works against.
Sub-membrane depressurization
Sheeting is laid across the entire soil surface, seams are overlapped and sealed, and the material is sealed to foundation walls and around piers. Suction piping is placed underneath the membrane so the fan holds the space below the sheeting at lower pressure than the crawl space above.
Soil gas is drawn into the space under the membrane rather than diffusing upward into the building.
What makes a membrane installation succeed
- Full coverage of the soil surface, including tight and awkward corners.
- Overlapped, sealed seams that hold over time.
- Sealing at foundation walls and around every pier and column.
- Sealing around plumbing, ducts and other penetrations through the soil area.
- Material durable enough for the traffic the crawl space actually gets.
- Piping placed so suction is distributed, not concentrated in one corner.
Fan, piping and exhaust
As with slab systems, the fan sits outside occupied space and the exhaust terminates above the roofline. Piping routes out of the crawl space through the rim or a wall, then up the exterior or through the structure.
Homes with both a basement and a crawl space
| Situation | Design implication |
|---|---|
| Crawl space added to a slab or basement home | The two foundation areas may not communicate, so separate suction points can be required. |
| Crawl space open to the basement | The connection between the areas has to be understood before assuming one system serves both. |
| Multiple crawl areas under additions | Each area may need its own membrane and its own suction point. |
A mixed foundation is the most common reason a home needs more than one zone. Compare system types.
Cost factors specific to crawl spaces
- Soil surface area to be covered and sealed.
- Headroom and access — low clearance slows every step.
- Number of piers and penetrations requiring individual sealing.
- Removal of debris or stored items before work can begin.
- Whether more than one crawl area exists.
Testing a crawl space home
Testing follows published guidance for the lowest lived-in level of the home rather than being placed in the crawl space itself. After installation, a follow-up test documents whether the system achieved the intended reduction.
Request crawl space mitigation quotes
Share your test result, foundation type and project details. We pass your request to independent radon professionals — we do not perform the work ourselves.