Crawl Space Radon
Crawl Space Radon Mitigation in Northern Colorado
An exposed-soil crawl space can be a major radon entry source because the building sits directly above a large soil surface. The effective solution is usually sub-membrane depressurization: isolate the soil with a durable gas-retarder membrane and apply suction beneath it.
A loose sheet of plastic is not the same as a radon system. Long-term performance depends on membrane material, seam construction, wall and pier attachment, penetrations, access, collection piping, fan selection, drainage, monitoring, and post-installation testing.
Request a Crawl-Space EvaluationWhat a Complete Crawl-Space System Includes
- Assessment of crawl area, height, access, soil, debris, standing water, drainage, utilities, piers, walls, and existing barriers
- Durable membrane suitable for long-term soil-gas control and crawl-space conditions
- Sealed seams and terminations at walls, columns, piers, pipes, ducts, supports, and access points
- Collection piping or suction points beneath the membrane
- Radon vent piping, fan, power, monitoring or alarm, labels, and compliant discharge
- Coordination with basement or slab zones in mixed-foundation homes
- Post-mitigation testing and long-term retesting
Why Membrane Details Matter
Seams
Overlaps must be constructed and sealed so normal movement, service traffic, and pressure do not open a soil-gas pathway.
Walls and Piers
The membrane must terminate securely at foundation walls and wrap or seal around supports. A perimeter that lifts away can short-circuit the system.
Penetrations
Plumbing, ducts, wires, posts, drains, and irregular masonry require durable details rather than temporary tape alone.
Access
The crawl must remain serviceable. Access panels, mechanical equipment, drains, and future repairs should be planned without sacrificing the gas barrier.
Moisture
Radon control and water management must work together. Standing water, groundwater, plumbing leaks, and poor drainage should not be hidden beneath a membrane without a plan.
Mixed Crawl Space and Basement Homes
Many Northern Colorado homes have a basement slab connected to one or more crawl spaces. The foundation wall between them may isolate pressure. A licensed designer determines whether the zones can share a fan, need separate suction points, or require independent systems.
Crawl-Space Cost Factors
- Square footage and crawl height
- Amount of debris, old plastic, insulation, and stored material that must be moved or removed
- Number of piers, walls, penetrations, and irregular edges
- Standing water, drainage, sump, or moisture work
- Foundation zones and number of suction connections
- Interior, garage, attic, or exterior pipe route
- Electrical access and fan location
Drennen 2026 crawl-space and mixed-foundation records commonly fall above straightforward slab-system pricing. Many ordinary crawl or mixed projects plan around the low- to mid-$2,000s, while large or difficult systems can cost much more. See the dedicated cost page for current ranges.
Common Shortcuts to Avoid
- Using thin or damaged plastic as the final radon membrane
- Leaving seams, walls, piers, or penetrations open
- Ignoring water or drainage beneath the membrane
- Applying suction above the membrane instead of beneath it
- Assuming one crawl suction point automatically communicates with a separate basement slab
- Finishing the system without a monitoring device or post-mitigation test
Frequently Asked Questions
Build the Barrier and Suction System as One Assembly
Drennen designs the membrane, collection, vent, fan, monitoring, and testing as a complete system and coordinates mixed foundations when present.
Request a Crawl-Space Radon QuoteA crawl-space membrane is part of a regulated radon system when installed for mitigation. Use a licensed Colorado Radon Mitigation Professional and confirm moisture, electrical, permit, and local requirements.
Drennen Custom Contracting | Serving Fort Collins and Northern Colorado | 970-482-9100 | [email protected]