Radon mitigation in the Denver metro
Denver metro mitigation runs into something most markets do not have: houses built with a structural floor over a void rather than a slab on grade, because the claystone beneath would heave a slab apart.
Denver holds a deep prewar stock of brick bungalows and Denver Squares on the near-north and near-east sides, many with garden-level basements or crawlspaces. Lakewood, Arvada, Aurora, and Littleton carry an enormous postwar ranch and split-level belt. Highlands Ranch and the southern suburbs are 1980s-forward construction, much of it built to deal with expansive claystone.
What mitigation involves here
A structural floor creates a crawl-height void between the living space and the soil, and that void is the soil-contact zone. Mitigating it is not sub-slab depressurization — it is void depressurization, often with a sealed membrane over the exposed soil and suction drawn beneath it. Done well it works excellently, because a membrane over open ground gives a fan a large, uniform area to pull from. Done as an afterthought on a quote written for a slab house, it does not work at all. Ask any Front Range bidder to identify your foundation type explicitly before quoting. Expansive soils shaped local building practice in ways that matter directly for radon. Structural floors over a void space — a suspended floor with a crawl area beneath, rather than a slab poured on grade — are common in the southern suburbs where claystone heave is severe. That void is a soil-contact zone with its own mitigation approach, and it is not something a standard sub-slab design addresses.
Deciding whether you need it
Whether a specific house in the Denver metro needs a system is settled by a measurement at that address, never by a county map — EPA recommends fixing at 4 pCi/L and considering action between 2 and 4 pCi/L. Requests from Denver & Jefferson, Arapahoe & Douglas, and Adams & Broomfield route to independent businesses that hold a current NRPP or NRSB mitigation certification; because Colorado does not issue its own radon license, that national certification is the credential to verify. The metro sits in the Denver Basin on the Denver Formation and Dawson Arkose — sediments shed east off the Front Range, carrying granitic material with them — over the Pierre Shale. The arkosic sands are permeable, and the Pierre Shale beneath is the bentonitic claystone responsible for the region’s notorious heaving soils. Both the source material and the pathways are locally abundant.
Who may legally do the work
Colorado does not license radon professionals at the state level. The state radon program instead directs homeowners toward nationally certified professionals credentialed through NRPP or NRSB. Ask any bidder which national certification they hold, confirm it is current, and apply the same scrutiny to the written design, warranty terms, and whether a post-mitigation verification test is included.
Communities we route in Denver Metro
Radon Mitigation questions in Denver Metro
Our house has a structural floor with a crawl space under the main level. What does that mean for a system?
It means the design is sub-membrane or void depressurization rather than sub-slab. A contractor seals a membrane over the exposed soil in the void, draws suction beneath it, and routes to a fan outside conditioned space. It is a well-understood approach and often performs very well. What it is not is the same job as coring a basement slab, so make sure your quote describes the foundation you actually have.
What makes mitigation different in the Denver metro?
Postwar ranch neighborhoods have generous lots and easy exterior routing. Prewar Denver bungalows have narrow lots, alleys that often provide a discreet rear route, and crawlspaces rather than full basements. Newer southern-suburb housing has HOA appearance rules and structural-floor voids that need their own access.
Does Radon Connect do the mitigation work?
No. Radon Connect is a free referral service — it does not test, inspect, design, or install anything. Your request goes to no more than three independent businesses serving the Denver metro, each holding a current NRPP or NRSB mitigation certification, and each quotes you directly. The contract, the price, the schedule, and the warranty are between you and the contractor you pick.
Related Denver Metro guides
- Radon testing in Denver Metro
- Mitigation cost in Denver Metro
- Failed a radon test in Denver Metro
- System installation in Denver Metro
- Colorado radon contractors: join our network
Decision guides for this stage
- How to choose a radon contractor
- What makes a great mitigation system
- Questions to ask before hiring
- All homeowner decision guides
The Denver metro runs through 3 routing territories — Denver & Jefferson, Arapahoe & Douglas, and Adams & Broomfield — with 6 community guides underneath them. Tell us your ZIP and we will either route it or say plainly that we cannot, and either way you keep the quotes and owe nothing.
Sources
- U.S. EPA — Radon
- U.S. EPA — A Citizen’s Guide to Radon
- U.S. EPA — Consumer’s Guide to Radon Reduction
- U.S. EPA — EPA Map of Radon Zones
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