Radon for Builders
Colorado Radon Requirements for Builders and Contractors
Radon rough-ins often cross several trades: excavation, foundation, plumbing, electrical, concrete, framing, roofing, insulation, air sealing, and mechanical. That does not make radon work an unregulated collection of trade tasks. Colorado regulates the design, installation, repair, modification, and professional measurement of radon systems.
The most expensive radon failures are often created long before anyone installs the fan. Missing collection material, divided foundations, unsealed membranes, buried piping errors, inaccessible cleanouts, poorly planned chases, fan locations inside conditioned space, and unsafe discharge routes can turn an inexpensive rough-in into a difficult retrofit.
A builder, plumber, electrician, HVAC contractor, concrete contractor, or general contractor is not automatically authorized to perform professional radon mitigation. The radon work must be performed by a Colorado-licensed Radon Mitigation Professional or by personnel working under the direct supervision required by Colorado law.
What Colorado Regulates
Colorado law defines radon mitigation broadly enough to include installing, repairing, and modifying a system. The state also separately regulates professional radon measurement. Since July 1, 2022, individuals practicing either service must hold the applicable Colorado license unless a statutory exemption applies.
- Radon system design and selection of the control method
- Installation of soil-gas collection, vent piping, fans, monitoring, labels, and discharge components
- Crawl-space membrane and sub-membrane depressurization work
- Activation of a passive system and modification of an existing system
- System repair, rerouting, fan changes, and performance troubleshooting
- Professional radon testing, including pre-occupancy, post-mitigation, transaction, and large-building measurement
Direct Supervision Is Not a Paper Sign-Off
Colorado allows trained assistants to perform radon tasks under direct supervision. The responsible licensed professional must supervise in the manner defined by the Radon Professionals Practice Act. Builders should identify the responsible licensee before work begins and should not assume that a licensee can approve concealed work remotely after the concrete is placed or the walls are closed.
A subcontractor invoice showing a company name is not enough. Ask for the individual mitigation license number, current DORA status, who will supervise each phase, and who will sign the system documentation.
The Standards Colorado Currently Incorporates
Colorado rule 4 CCR 754-1 incorporates specific editions of national consensus standards. The incorporated edition matters because newer industry editions do not automatically replace the edition named in the state rule.
RRNC-2020
Rough-in Radon Control Components in New Construction of 1 & 2 Family Dwellings and Townhouses. This addresses passive rough-in components before activation.
CCAH-2020
Reducing Radon in New Construction of 1 & 2 Family Dwellings and Townhouses. This addresses completed radon control systems and active performance in new low-rise residential construction.
CC-1000-2018
Soil Gas Control Systems in New Construction of Multifamily, School, Commercial, and Mixed-Use Buildings.
SGM-SF-2017
Soil Gas Mitigation for Existing Homes. This becomes important when a rough-in is incomplete, a new home tests high, or the passive system must be corrected or activated.
RMS-MF-2018 and RMS-LB-2018
Mitigation standards for multifamily buildings and for schools and large buildings.
State Licensing Does Not Mean Every New Home Has the Same Radon Code
Colorado licenses radon professionals statewide, but local jurisdictions decide whether their adopted building code requires radon-resistant new construction, active mitigation, testing, or specific inspections for a particular project. Unincorporated Larimer County, for example, states that newly constructed dwelling units require a radon mitigation system and radon testing. Other jurisdictions may apply different requirements.
The project team should confirm the authority having jurisdiction, adopted code edition, local amendments, plan-review notes, permit type, inspection sequence, electrical requirements, and required documentation before construction. The radon professional should then design to the applicable local requirements and the Colorado-incorporated standard.
Components Builders Commonly Miss
Continuous Soil-Gas Collection
The collection layer or plenum must communicate across the foundation area. Footings, grade beams, thickened slabs, elevator pits, additions, and isolated pods can block pressure-field extension.
Foundation-Specific Planning
A slab, basement, crawl space, and mixed foundation do not use identical details. Each ground-contact zone needs a deliberate collection strategy.
Crawl-Space Membrane
A loose vapor barrier is not automatically a radon membrane system. Material, seams, wall attachment, piers, penetrations, terminations, access, and suction connection must work as one gas-control assembly.
Sump and Drain Details
Open or loosely covered sumps can become major soil-gas pathways. Covers, penetrations, drainage function, future service, and labels must be coordinated rather than improvised at turnover.
Pipe Size and Coverage
Pipe sizing and the area served by a rough-in must follow the applicable standard. One small stack should not be assumed to serve an unlimited slab area or multiple isolated foundations.
Chase and Route
The route must remain continuous, accessible where required, protected from damage, and coordinated with fire blocking, insulation, structure, plumbing, electrical, and future fan installation.
Fan Location
An active fan is generally located outside conditioned or occupiable space, such as outdoors or in an approved attic or garage location that does not place the positive-pressure side through living space.
Discharge and Re-Entry
The exhaust must terminate where radon cannot readily re-enter windows, doors, soffits, balconies, rooftop equipment, or adjacent occupied areas. The route cannot be decided only for appearance.
Electrical and Alarm
Plan a code-compliant power source, service access, disconnect as applicable, monitoring or alarm, and a route that does not force unsafe extension cords or inaccessible equipment.
Labels and Turnover Documents
Identify the stack, fan circuit, monitoring device, system purpose, responsible professional, test result, warranty, and operating instructions. Future owners and service technicians should not have to guess.
Recommended Construction Sequence
- 1
Design before excavation and foundation work
Map foundation zones, collection strategy, penetrations, sump and drainage, stack location, fan location, discharge, electrical, inspection points, and future service access.
- 2
Install the collection plenum
Place clean aggregate, geotextile collection mat, perforated piping, or the specified assembly before the slab or membrane conceals the work.
- 3
Inspect before concealment
Photograph and verify collection continuity, stub-ups, caps, pipe protection, membrane transitions, and isolated foundation zones before concrete or finishes prevent correction.
- 4
Complete the gas-control barrier
Seal the slab and penetrations as specified, or install and seal the crawl-space membrane as a system. Coordinate drainage and moisture rather than trapping water.
- 5
Complete the vertical stack and rough electrical
Maintain the required pipe size, slope and support, labels, clearances, service access, and future fan provisions.
- 6
Test the building
A passive rough-in is not proof of performance. Test the completed building under the applicable protocol after conditions are suitable.
- 7
Activate or correct if needed
If the result is elevated, the licensed professional selects the fan, checks pressure-field extension, corrects deficiencies, and completes active-system documentation.
Common Builder Failure Scenarios
The passive stack was never connected
A pipe visible in the attic or mechanical room may terminate in gravel, a wall cavity, or nowhere useful.
One stack serves disconnected slabs
Footings or additions isolate pressure zones, so the fan pulls from one area while radon enters through another.
The fan is planned inside living space
This creates an inappropriate positive-pressure radon-pipe condition and can complicate noise, service, and safety.
The crawl membrane is treated like ordinary poly
Loose edges, unsealed piers, torn seams, and open penetrations prevent the system from creating a reliable vacuum beneath the soil barrier.
The roofer or plumber finishes the stack without radon coordination
The resulting termination may create re-entry, condensation, snow, structural, flashing, or service problems.
Testing is delayed until after turnover
The buyer discovers an elevated result after closing, when corrective routing is more disruptive and responsibility is disputed.
Builder and Contractor Checklist
- Confirm the local AHJ requirements and adopted code before plans are finalized
- Retain a currently licensed Colorado Radon Mitigation Professional
- Identify the licensed person responsible for direct supervision of every concealed phase
- Show foundation zones, collection, stack, fan, electrical, alarm, discharge, and access on coordinated plans
- Schedule pre-slab or pre-concealment review before correction becomes expensive
- Protect radon components during later trade work
- Test the completed building under the applicable licensed measurement protocol
- Deliver system diagrams, photos, licenses, test reports, warranty, and operating instructions at turnover
Drennen New-Construction Support
Drennen can review plans, identify foundation zones, prepare radon-control details, coordinate soil-gas collection and membranes, inspect concealed work, plan pipe and fan routes, activate passive systems, conduct licensed testing, and provide turnover documentation. Early involvement is usually less expensive than correcting a finished building.
Request Builder Radon PlanningReviewed July 2026. This page is general education, not project-specific design, engineering, code interpretation, or legal advice. The current Colorado rule, incorporated standard, local code, permit documents, and authority having jurisdiction control.
Drennen Custom Contracting | Serving Fort Collins and Northern Colorado | 970-482-9100 | [email protected]