Introduction
Radon rough-in means running piping and electrical raceways into the slab area now so you can add a full mitigation fan and finish the system later; full mitigation means installing the active fan, routing the exhaust and testing after the slab and interior are complete. This gives you a choice at pour time: save the slab penetrations and plan vent paths, or complete the whole system if testing shows it’s needed. Think like a foreman—mark the stack location, keep access above the slab, and check product labels and local rules for pipe size, slope, and sealing details.
Radon is a health risk when it accumulates in living spaces, so planning vent paths before the pour is a practical safety step for DIYers. Test the house after it’s habitable to decide if the rough-in is enough or if you must add an active fan and finish the exhaust run. If you’re unsure about specs or regulations, check manufacturer instructions and local building or environmental guidance before you buy or install anything.
Key takeaways
- Plan vent paths early to ensure reliable exhaust routes and prevent rework.
- Rough-in allows future testing; confirm access, clean penetrations, and airtight seals.
- Install proper seals at slab penetrations and joints to minimize entry.
- Test radon pre-build and post-pour to inform mitigation strategy choices.
- Design vent paths before pour with routing, penetrations, and airtight detailing and safety precautions.
- Consider full mitigation options during construction for easier integration later.
- Know permits, inspections, and when to hire a professional for compliance.
Table of Contents
- Introduction
- Key takeaways
- Rough-in Vs Full Mitigation — Definitions and Decision Framework
- Health Risks and the Importance of Planning
- Testing Strategy for New Construction: Pre-Build, During, and Post-Pour
- Designing Vent Paths Before the Pour — Routing, Penetrations, and Airtight Details
- Rough-in Installation Workflow and DIY Checkpoints
- Full Mitigation Under New Slabs — ASD Methods and Membrane Systems
- Costs, Timing, and Lifecycle Tradeoffs
- Permits, Inspections, Standards, and Hiring a Professional
- Conclusion
- FAQ
Rough-in Vs Full Mitigation — Definitions and Decision Framework
For slab-on-grade work a “rough-in” means laying out the future radon exhaust paths before the concrete goes down: install sleeves or short risers through the slab, place sub-slab openings or sumps, run stubbed piping and mark perforated lines so an active system can be added later. Typical rough-ins use durable, code-accepted piping and temporary seals; check the product label or manufacturer instructions for compatible sleeve sizes and materials.
“Full mitigation” at pour is installing an active sub-slab depressurization system (ASD) now—complete vent piping, fan location, continuous exhaust stack, membrane or vapor barrier integration, commissioning, and monitoring. Choose based on site risk (local soil/radon potential), existing test results, occupancy and remodel plans, and budget; if in doubt, get baseline testing and a third-party opinion to guide whether rough-in or full ASD is appropriate.
What a Radon Rough-In Includes
A radon rough-in is like planning the route for your future radon system. It’s not complete, but it sets things up so you can finish later.
Here’s what’s typically involved:
Sub-slab pipe stub-ups: These are pipes that stick out from under where your slab will be. They’re ready for the fan and vent stack to connect later.
Membrane terminations: A special barrier goes under your slab to keep radon from coming up. The rough-in includes ends for this membrane so it can be sealed when you finish the system.
Stubbed risers: These are pipes that go through your slab, ready for the fan and vent stack to connect on top.
What Full Mitigation Under a New Slab Entails
Full mitigation is like installing your entire radon system before the slab goes down. It’s complete and ready to go.
Here’s what you get:
Active soil depressurization (ASD) fan: This fan sits in your basement, pulling radon out from under your slab.
Sealed penetrations: Pipes and wires go through your slab and foundation walls. They’re sealed to keep radon out until the system is running.
Exterior exhaust routing: The pipe that carries radon away from your home sticks out of the ground, usually at least 10 feet from any windows or doors. It’s ready for the fan to start pulling.
When to Choose Rough-In vs Full Mitigation
The choice between a rough-in and full mitigation depends on several factors. Here’s what to consider:
Site radon risk: If your soil has high radon levels, you might want full mitigation right away. If it’s low, a rough-in could be fine.
Test history: If previous tests show high radon, go for full mitigation. If they’re low, a rough-in might be okay.
Construction schedule: If you’re in a hurry to move in, full mitigation can save time later. But if you’ve got time, a rough-in could be cheaper upfront.
Cost tradeoffs: A rough-in is cheaper now but costs more later when you finish the system. Full mitigation is more expensive now but less later.
Local code requirements: Some places require full mitigation. Check your local codes before you decide.
Health Risks and the Importance of Planning
Radon is a long-term inhalation hazard that accumulates indoors; reducing entry at the slab greatly reduces lifetime exposure compared with retrofits after occupancy. Early planning during slab construction limits pathways, simplifies routing, and reduces the invasive work needed later.
Decisions made now—number and placement of sumps, whether to leave active versus passive venting options, and routing of sub-slab lines—affect future system performance and costs. Coordinate who designs and who tests the work, verify testing schedules and limits with the testing protocol or product data sheet, and plan for post-pour testing and routine monitoring once systems are active.
Radon exposure and health implications
Radon is a colorless, odorless gas that can seep into your home through cracks in the foundation or slab. It’s linked to lung cancer – the leading cause of cancer deaths among non-smokers.
Key point: Radon exposure isn’t something you can see or smell, so measuring it is crucial. Check national health guidance for action levels – typically around 100-200 Bq/m³.
Long-term exposure to even low levels of radon increases your risk of developing lung cancer. Don’t guess; test and mitigate as needed.
How slab and foundation choices affect long-term indoor radon
The thickness, penetrations, drains, and soil conditions around your slab can change how radon enters your home. Thicker slabs and fewer cracks help, but they’re not foolproof.
Key point: Sealing and routing vents before pouring the slab is crucial to minimize entry points and ensure proper venting.
Soil conditions also play a role. Radon-prone areas may require additional measures. Consult local building codes or experts for guidance.
Testing Strategy for New Construction: Pre-Build, During, and Post-Pour
Start with a baseline site assessment before excavation to understand soil gas potential, then test again before choosing rough-in versus full mitigation; after system installation perform mandatory post-mitigation testing to confirm performance. Use the test types appropriate to each stage—soil-gas screening, short-term air tests, or continuous monitors—and check manufacturer instructions or testing protocol for device placement and duration.
At each stage target different metrics: pre-build soil-gas and geology, pre-pour pressure differentials and slab sealing checks, and post-installation indoor radon concentrations and system suction performance. Assign responsibilities up front—owner, contractor, or certified tester—collect documentation for permits, and follow local codes or industry guidelines for acceptable action levels and retest timing.
Long-term vs short-term testing considerations
Long-term tests, like charcoal canisters left out for a few days to a week, give the most accurate estimate of your home’s average radon exposure. They’re ideal for making informed decisions about mitigation levels.
Short-term tests, using continuous monitors over 48 hours, are quicker but less precise. Use them early on to decide whether to hire a professional or place test kits.
Pro tip: Long-term tests should still be done after any major changes to your home, like finishing a basement or installing a new HVAC system.
Where and when to test on slab projects
For new slabs, test before pouring. Place test kits at the lowest lived-in level, like a basement or first floor. Wait until after HVAC systems are installed and running for accurate readings.
After mitigation, retest once the system’s been active for at least 24 hours. Make sure to test in the same location as before.
Remember: Radon levels can change over time due to factors like soil moisture or foundation settling. Regular follow-up testing is crucial.
Designing Vent Paths Before the Pour — Routing, Penetrations, and Airtight Details
Map living and utility zones to place vent routes that are as straight and short as possible while avoiding rebar, buried utilities, and structural conflicts; prioritize runs that minimize through-wall or through-floor penetrations. Select sleeve sizes and locations and confirm sleeve and seal details against manufacturer instructions or job-specific drawings.
Specify sleeves, grommets, and fire/smoke-rated seals where pipes pass walls or footings and plan redundant airtight seals at slab edges and around transitions to the vapor barrier. Create coordination drawings, schedule inspection points for sleeving and sealing prior to pour, and document as-built locations to make later activation straightforward.
Sub-slab vent routing principles
Plan your vent pipe route before the slab pour. Keep it simple and practical.
Shortest runs: Go for straight, short routes to minimize resistance. Avoid long, winding paths.
Avoid sharp bends: Sharp turns can restrict airflow. Stick to gentle curves or 90-degree elbows.
Slope if needed: If required, slope the pipe slightly towards the exhaust point. But keep it accessible for future fan installation.
Integrating sumps, drainage, and membrane terminations
Tie in your vent system with existing structures. Seal them tight to prevent leaks.
Sump pits: Locate sump pits near the lowest point of your slab. Seal around the pipe to stop radon ingress.
Drainage systems: Connect your drainage to the vent system. Prevent water from creating leak paths.
Vapor barrier termination: Terminate your vapor barrier at planned penetrations. Seal it tight to maintain the air barrier.
Exterior exhaust, riser placement, and locating the fan
Route your exhaust pipe outside. Place your risers and fan for easy access.
Exhaust route: Run the exhaust clear of windows and air intakes. Avoid areas where radon could re-enter the home.
Riser placement: Place risers through walls or roofs, following local codes. Keep them accessible for future maintenance.
Fan location: Locate your fan outside, away from living spaces. Make it easily accessible for service and code compliance.
Rough-in Installation Workflow and DIY Checkpoints
Begin with a pre-pour compliance checklist: confirm permits, review local code requirements, and verify vent path sizing and material specs against product labels or local AHJ guidance. Lay out rough-in locations, install sleeves and stub risers, and protect openings during pour while clearly labeling each component for future connection.
Define clear contractor versus DIY responsibilities and capture as-built photos and a simple diagram showing vent runs, access points, and cleanouts. Use staged checkpoints—sleeve placement, seal integrity, protection during pour—and assemble an inspection-ready packet with photos and notes to hand to the mitigator or inspector later.
Tools and visual checkpoints at rough-in stage
Before pouring, use this checklist to ensure your radon rough-in is ready. Here’s what you need to do:
- Pipe alignment: Check that vent pipes are straight and aligned with each other.
- Membrane continuity: Ensure the gas barrier membrane is intact and sealed around pipe penetrations.
- Labeled stubs: Mark all vent lines, cleanouts, and access points for easy identification post-pour.
- As-built diagrams: Capture drawings of your rough-in layout for future reference.
- Accessibility: Confirm that all components are accessible for post-pour installation and testing.
- Stack heights: Measure and record the height of each pipe stack to ensure they meet code requirements.
- Connection points: Verify that all connections to future active depressurization systems (if needed) are properly prepared.
- Safety check: Ensure there are no sharp edges or hazards that could pose a risk during the pour.
Quick rule: A thorough visual inspection and record-keeping at this stage can save you from costly rework later on.
Common DIY rough-in steps and when to call a pro
Here’s what you can do yourself, and when it’s time to bring in the pros:
- Basic routing: You can lay out simple vent paths following the principles discussed earlier.
- Penetrations: Create openings through framing members for your vent pipes.
- Labeling: Mark all components as per your as-built diagrams.
- Temporary protection: Cover exposed rough-ins to prevent damage during the pour.
- Large soil gas leaks: If you encounter significant soil gas emissions, stop and call a certified mitigator. They have specialized equipment for such cases.
- Complex routing: If your vent path design is intricate or involves multiple levels, consider hiring a pro to ensure it’s done right.
- Code obligations: Always consult local codes and get necessary permits. If unsure, hire a professional to guide you through the process.
Quick rule: Know your limits. DIY is great for simple tasks, but complex jobs or code-related issues are best left to professionals.
Full Mitigation Under New Slabs — ASD Methods and Membrane Systems
Full mitigation for new slabs covers ASD options that create negative pressure beneath the slab via suction points, centralized fans, and continuous piping routed to exterior discharge; plan fan siting, stack routing, and electrical needs before pour. When using a membrane system, coordinate seam layout, skirt sealing, and under-membrane depressurization details per the membrane manufacturer’s installation instructions.
Specify appropriate materials—perforated sub-slab pipe, HDPE or approved membrane types—and detail sealing methods at seams, penetrations, and slab edges to prevent leaks. Include a stepwise plan: site assessment, placement of suction zones, integration with slab pour schedule, inspection milestones, and post-pour performance testing and monitoring arrangements.
Active sub-slab depressurization options
ASD systems create negative pressure under the slab to draw radon out. The main configurations are:
Single-point: One suction point pulls air from a central location, best for low permeability soils and small footprints.
Multi-point: Multiple points spread across the slab, ideal for high permeability soils or large houses to maximize coverage.
Sealed slab approaches use a continuous membrane under the slab. Membrane approaches combine a membrane with perforated piping. Choose based on soil permeability and house size.
Drainage, membrane, and slab-sealing best practices
Proper sealing reduces leakage paths, enhancing ASD performance:
Membranes: Use continuous membranes to seal the underside of the slab. Seal construction joints with caulk or tape.
Drainage: Tie in drainage systems to carry away water that seeps through cracks or around pipes, preventing backflow and condensation issues.
Slab sealing: Seal all penetrations, including plumbing and electrical chases, using caulk or foam sealant. Coordinate with your pour schedule to ensure proper reinforcement placement.
Costs, Timing, and Lifecycle Tradeoffs
Choosing rough-in now reduces future invasive costs and downtime but delays fan and full-system expense; installing full mitigation at pour adds upfront cost and schedule coordination but minimizes retrofit disruption later. For budgeting, verify exact cost items and timelines with contractors or product quotes rather than relying on rough estimates.
Align rough-in or full-system work with slab scheduling to avoid delaying the pour and to ensure inspections occur when sleeves and seals are accessible. Build lifecycle expectations into the decision—maintenance, monitoring, and possible upgrades—and document acceptance criteria, warranties, and re-test plans in the contract.
Budget planning and cost drivers
Planning your radon mitigation system’s budget starts with understanding the primary cost drivers. Here are the key factors to consider:
Fan type and location: Inline fans are cheaper but less efficient than ECM fans. Fan placement affects piping length, impacting costs.
Piping length and membrane quality: Longer runs mean more material. Better membranes cost more but last longer.
Labor and permitting: Labor accounts for a significant portion of the cost. Permitting fees vary by location.
Long-term maintenance and energy considerations
Maintaining your radon mitigation system is crucial to keep it running efficiently and safely. Here’s what you need to plan for:
Routine fan checks: Inspect the fan annually to ensure it’s running smoothly. Clean or replace as needed.
Sealing inspections: Check seals around pipes, membranes, and sumps every few years to prevent radon entry points from forming.
HVAC impacts: Radon mitigation systems can slightly increase energy bills due to the fan’s operation. Plan for this minor impact on your HVAC system.
Permits, Inspections, Standards, and Hiring a Professional
Check with the AHJ early about permit needs, required inspections at pre-pour and final stages, and any local standards that must be met; include required drawings and test protocols in permit submissions. Reference recommended industry practices or state guidelines when preparing submittals, and confirm any product compliance on the manufacturer data sheet.
Vet mitigators by checking licenses, insurance, references, and a clear written scope of work with change-order procedures and warranty language. Prepare a pre-pour coordination plan that lists inspection milestones, required documentation, and post-pour testing responsibilities so everyone knows who signs off at each stage.
Typical regulatory and inspection requirements
Before you start any work, use this checklist to understand what’s required in your area.
- Check local building codes: Ensure your plan complies with local regulations. Skipping this can lead to costly rework or permit denials.
- Required permits: Know which permits are needed for your specific project. Without them, you could face fines or delays.
- Pre-pour inspection: Coordinate with the Authority Having Jurisdiction (AHJ) to schedule this before pouring the slab. It ensures everything is set for a smooth pour and helps avoid delays.
- Rough-in inspection: Schedule another inspection once the rough-in work is complete. This confirms everything is installed correctly before the slab goes in.
- Final inspection: Plan for a final inspection after mitigation is complete. It ensures your system meets code and functions properly.
- EPA/NRPP/NRSB guidelines: Familiarize yourself with these standards to ensure your plan meets federal recommendations. Ignoring them can lead to ineffective systems or non-compliance.
- AHJ contact info: Keep the AHJ’s contact details handy for quick reference and easy coordination. Not having their number can cause delays if issues arise.
- Inspection fees: Know what fees are involved with each inspection. Being unaware of costs can lead to unexpected expenses.
Quick rule: Always communicate openly and regularly with the AHJ to avoid surprises and keep your project on track.
How to choose and verify a certified radon professional
Before hiring, follow this checklist to ensure you’re working with a qualified mitigator.
- Check certifications: Ensure they hold current EPA/NRPP or NRSB certifications. Working with an uncertified pro can result in ineffective systems and costly rework.
- Ask for references: Request contact info for at least three recent clients. Talking to past customers gives insight into the pro’s work quality and reliability.
- Review sample contracts: Ask to see a sample contract outlining their scope of work, warranties, and change-order processes. This helps you understand what you’re paying for and ensures expectations are clear.
- Performance guarantees: Ensure they offer a performance guarantee in writing. A reputable pro will stand behind their work.
- Post-installation testing: Confirm they’ll conduct post-installation testing to ensure the system works as expected. Without this, you won’t know if the system is effectively mitigating radon.
- Licenses and insurance: Verify they hold all necessary licenses and carry adequate liability insurance. Working with an uninsured or unlicensed pro can leave you vulnerable to financial loss or legal issues.
- Experience in your area: Preference should be given to pros with experience working in your specific region. Local knowledge can lead to more effective and efficient mitigation.
- Communication style: Ensure they communicate clearly and promptly, as you’ll need to coordinate throughout the project. Poor communication can cause delays or misunderstandings.
Quick rule: Never hire a mitigator based solely on price. Quality and reliability are more important in the long run.
Conclusion
Before you pour, lock in a straight path for radon that will stay robust for the life of the slab. A clear plan now saves you from blowing money on rework, and it keeps your family safe from indoor air issues down the road.
First, decide on rough-in versus full mitigation, map your vent routes, and confirm your pre-pour testing plan, penetrations, and airtight details. Stick to a simple, stepwise flow: finalize the design, verify permits and inspections, lay out vent paths with minimal penetrations, seal joints, run a dry fit, and then test in a small area before you pour. If you’re unsure about ASD methods, membrane systems, or complex routing, lean on professional guidance early.
Common mistakes to avoid are skipping the planning phase, underestimating the number of penetrations, and patching leaks after the concrete is in. Don’t cut corners on sealing and air barriers, and don’t skip pre-pour testing or a small-area trial. Follow the safety rule: test early, test often, and don’t compromise the slab or its edge details.
When to call a pro is clear: if the site is difficult, if the plan touches membrane systems or ASD methods, or if permits and inspections feel like a trap you can’t navigate. A professional helps you avoid costly mistakes and keeps the schedule realistic. Stay focused, stay safe, and you’ll keep the project moving without compromising long-term performance.
FAQ
What is the health risk if radon is present in a new home, and why plan early?
Radon is a radioactive gas that can build up indoors. Long exposure increases the chance of lung issues, especially in homes with poor ventilation. Planning vent paths early helps you control where it goes and how it behaves before concrete locks you in.
How can I detect radon levels during or after construction, and what should I look for in tests?
Use testing methods designed for new construction and post-pour scenarios. Look for test kits or professional tests that specify short-term and long-term options and follow their placement guidelines. Always check the manufacturer’s instructions and local requirements for testing accuracy.
What does rough-in radon mitigation look like during the build, and what should I verify in the plan?
Plan vent paths, penetrations, and airtight connections now. Verify that proposed vent routes, seals, and sleeve placements match the final slab design. If in doubt, check labels and manufacturer instructions for any components you plan to use.
What should I know about legal or inspection requirements for radon control in new buildings?
Requirements vary by area. Check local rules, building department guidance, and any permit conditions. Rely on official instructions and approved plans to ensure you meet what inspectors will expect on the day of review.