DIY Radon Mitigation: Complete Installation Guide (Slab & Crawl Space)

Before You Start: Is Your Home a DIY Candidate?

Sub-slab depressurization (SSD) is straightforward on the right home. Check these before buying anything:

Good DIY candidates:

• Slab-on-grade or basement on concrete slab
• Radon level under 15 pCi/L (confirmed by test)
• Accessible attic or exterior wall for pipe exit and fan mounting
• Single continuous sub-slab zone (no isolated sections under additions)

Get a professional instead if:

• Crawl space with severe access restrictions (under 18" clearance, standing water, mold)
• Radon above 15 pCi/L on first test — high levels need professional assessment
• Block wall foundation (requires different technique)
• Historic home with unusual construction
• You have no experience with power tools

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Safety First — Read This Before Touching Anything

The #1 hazard isn't radon — it's silica dust

Drilling through concrete generates crystalline silica dust. Short-term radon exposure during construction is not a health concern. Silica dust is. A single unprotected drilling session can cause lasting lung damage.

Wear an N95 respirator (minimum) every time you drill. A paper dust mask is not adequate. An N100 or P100 half-face respirator is better. Wet the concrete slightly before drilling to suppress dust. Vacuum immediately after drilling — don't let dust settle.

Electrical safety

The fan requires a dedicated 110V circuit or a connection to an existing circuit near the installation point. If you're not comfortable with basic electrical work — running wire through walls, connecting to a junction box — hire an electrician for that step. Everything else can be DIY.

Turn off power at the breaker before making any electrical connections. Confirm with a non-contact voltage tester.

PVC primer and cement fumes

PVC primer (purple) and cement are highly flammable and produce strong VOCs. Work in ventilated areas. No open flames nearby. Keep the lid on when not actively applying.

Crawl space safety

• Wear a Tyvek suit or clothes you'll discard — crawl spaces are filthy
• N95 or better for dust and mold
• Knee pads — you'll be on them for hours
• Headlamp (hands-free)
• Have someone outside who knows where you are
• Never work in a crawl space with standing water — electrocution risk if any electrical is involved

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Tools You Need

For every installation:

• Hammer drill or rotary hammer — a standard drill won't cut through concrete reliably
• 3" diamond core drill bit (dry-cut) — for the suction hole through the slab
• Shop vac — for concrete dust, required
• Hacksaw or PVC cutter — for pipe cutting
• Level — for pipe runs and fan mounting
• Tape measure and pencil
• Caulk gun
• Drill with bits — for pipe hangers and fan mounting
• N95 respirator — non-negotiable
• Safety glasses
• Work gloves

For slab installs:

• Hydraulic cement (for sealing annular space around pipe)
• PVC primer and cement (or use gasketed connections)
• Electrical supplies — wire, wire nuts, junction box, conduit if needed

Additional for crawl space:

• Knee pads
• Headlamp
• Tyvek coveralls or disposable clothes
• Utility knife (for cutting vapor barrier)
• Heavy-duty staple gun (for securing barrier to wall)
• Caulk for wall-to-floor transition

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Part 1: Slab-on-Grade Installation

Step 1 — Confirm Sub-Slab Communication

Before you drill a 3" hole, spend 15 minutes confirming that suction will actually travel under your slab. Some homes have isolated sub-slab zones, packed clay with poor air movement, or full concrete fill.

The communication test:

1. Drill a small exploratory hole (½" or ¾") in the planned suction location
2. Insert a smoke pencil or incense stick in the hole
3. Cover the rest of the hole with your hand and create slight negative pressure (or use a small shop vac)
4. If smoke is drawn in easily, sub-slab communication is good
5. If nothing moves, try a different location

If you find poor communication at multiple spots, you may need more than one suction point — or a higher-suction fan. At this point, call a mitigator to assess.

Step 2 — Choose Your Suction Point Location

The best suction point location:

• Interior, centered under the slab — maximizes coverage
• Away from exterior footings — drilling too close to footings can compromise the foundation
• Near a wall with a clear path to the fan location above
• Away from plumbing and electrical — probe before you drill

Critical: Stay at least 12 inches from any exterior wall footing. Mark your location and use a wire detector to scan for embedded conduit or rebar before drilling.

Step 3 — Drill the Core Hole

1. Mark your spot clearly
2. Put on your N95 respirator before starting the drill
3. If possible, slightly wet the surface to suppress dust
4. Using your hammer drill and 3" diamond core bit, drill straight down through the slab. Go slow — let the bit do the work
5. Most residential slabs are 4"–6" thick. You'll feel the resistance change when you break through
6. Immediately vacuum the hole and surrounding area
7. Look into the hole with a flashlight — confirm you can see sub-slab material (gravel, dirt, or air gap)

Step 4 — Test Suction at the Hole

Before cutting any pipe, confirm the hole location is good:

1. Hold your hand over the hole — you should feel air being drawn upward from the sub-slab pressure differential
2. A manometer or smoke pencil confirms negative pressure
3. If you feel nothing, try a different location and re-drill

Step 5 — Route the Pipe

Plan your pipe run from the suction hole to the fan location before cutting anything.

Pipe routing rules:

• Fan goes outside the living space — in the attic, in an attached garage, or on an exterior wall. Never in a finished basement or living area. If the fan fails, you want it outside conditioned space.
• Keep runs short and straight — every 90° elbow adds resistance. Minimize bends.
• Slope horizontal runs toward the suction point at ¼" per foot so condensation drains back down rather than sitting in the pipe
• Support horizontal runs every 4–6 feet with pipe hangers screwed to joists

Dry-fit all pieces before gluing. Mark alignment with a pencil across joints so you can reproduce alignment after applying cement.

To glue PVC:

1. Clean and dry both surfaces
2. Apply purple primer to both the pipe end and fitting socket — let flash for 10 seconds
3. Apply cement to both surfaces
4. Push and twist ¼ turn — hold for 10 seconds
5. Wait 30 minutes before handling; 2 hours before applying any pressure

Step 6 — Install the Fan

Fan mounting options, in order of preference:

1. Attic — best for fan longevity (protected from UV and weather), quietest (vibration doesn't transmit to living space)
2. Exterior wall — common, easy to access, but fan is exposed to elements
3. Garage — good compromise if attic isn't accessible

Fan orientation: Most radon fans can be mounted in any orientation (vertical, horizontal, or angled) — check your specific model's installation manual. The suction port goes toward the sub-slab; discharge goes toward the outside vent termination.

Vent termination: The discharge pipe must terminate:

• At least 12" above the roofline or 10 feet from any window/door opening on the same wall (AARST-ANSI standard)
• Never under an overhang where exhaust can re-enter
• With a rain cap to prevent moisture and pest entry

Electrical connection: The fan needs 110V power. Options:

• Run a new circuit from the panel (cleanest)
• Connect to an existing nearby circuit via junction box (acceptable if circuit isn't overloaded — fans draw 20–50 watts)
• Use an outdoor-rated cord connection if permitted by local code

Wire the fan according to manufacturer wiring diagram. Most residential radon fans are simple: black to black (hot), white to white (neutral), green or bare to ground. Confirm with a voltage tester before and after.

Step 7 — Seal the Annular Space

This is the step most DIYers skip, and it matters.

The gap between the 3" pipe and the hole in the concrete (the annular space) is a direct radon pathway into the house. It must be sealed.

How to seal with hydraulic cement:

1. Mix hydraulic cement to a thick paste consistency (like peanut butter)
2. Pack it firmly into the annular space around the pipe from above
3. Smooth flush with the slab surface
4. Hydraulic cement sets in 3–5 minutes — work quickly
5. Allow 30 minutes of full cure before operating the system

Also seal any other slab penetrations you identified during your pre-install walkthrough: floor drain rims (use caulk or hydraulic cement), utility pipe entry points, sump pit (use an airtight cover — this is the largest single radon entry point in most basements), visible cracks in the slab (use polyurethane caulk or RadonSeal).

Step 8 — Install the Warning Device (Manometer)

Your system requires a visual indicator that the fan is operating and creating negative pressure. A U-tube liquid manometer is the standard — required by code in most states.

Install it on the suction pipe below the fan, at eye level, in a visible location. Follow the included instructions — typically this involves drilling a small hole in the pipe and inserting the sensing port.

Normal reading: The liquid column should show measurable differential pressure (the exact reading depends on your fan and sub-slab conditions). Check the manometer monthly. If the levels equalize, the fan has failed or a pipe connection has opened.

Step 9 — Power On and Initial Check

1. Turn on the fan
2. Check the manometer — confirm differential pressure is present
3. Hold your hand over every slab penetration you sealed — feel for air movement (there should be none after sealing)
4. Listen for the fan — it should be a steady, low hum. Vibration or rattling indicates a loose pipe hanger or connection

Step 10 — Post-Installation Testing

Do not skip this step. A system that looks correct can still underperform.

• 24-hour test: Run a short-term kit immediately after installation. Many labs offer 24-hour processing for post-mitigation tests.
• 30-day test: The more definitive result. Run a second short-term test 30 days after installation.
• Target: Below 4.0 pCi/L. Below 2.0 pCi/L is achievable in most homes.

If post-mitigation levels are still above 4.0 pCi/L:

1. Confirm the fan is running (check manometer)
2. Check all sealed penetrations with your hand — feel for air infiltration
3. Consider adding a second suction point
4. If levels are still above 4.0 pCi/L after two suction points, call a certified mitigator

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Part 2: Crawl Space Installation

Crawl space jobs have an additional critical step before the fan goes in: the vapor barrier. Without it, the fan draws from an open soil surface rather than a controlled sub-membrane zone, and performance suffers significantly.

Step 1 — Assess and Prepare the Crawl Space

Before any materials go in:

• Remove all debris, old insulation, construction scraps, standing water, and any organic material from the floor
• Identify and mark all plumbing penetrations, support posts, and utility runs
• Note the access hatch location — you'll be routing pipe out through it or through a wall

If you find significant mold, extensive pest damage, asbestos-containing material, or more than ½" of standing water anywhere, stop and get a professional assessment before proceeding.

Step 2 — Install the Vapor Barrier

Materials: ASTM E1745 Class A or B vapor barrier (6 mil minimum, 10 mil for rocky floors), seam tape, anchor stakes, and caulk.

Barrier installation process:

1. Start at the far end from the access hatch — you don't want to walk on freshly laid barrier
2. Unroll the barrier across the floor, cutting around posts and penetrations with a utility knife. Leave 6"+ of extra material at all edges
3. Overlap seams by at least 12" — more is better. Mark overlap edge with a pencil line before taping
4. Tape every seam with butyl vapor barrier tape — press firmly across the full width
5. Lap the barrier up the perimeter walls at least 6" (12" is better). Secure to the wall with construction adhesive, caulk, or staples, then tape the wall-to-floor transition
6. Seal around all posts and penetrations — use tape and caulk. These are the spots where sub-membrane suction leaks
7. Pin the barrier with anchor stakes every 2 feet along seams and perimeter

The goal is a nearly airtight membrane. The fan creates negative pressure under it, pulling radon away from the living space.

Step 3 — Install the Sub-Membrane Suction Point

The suction point for a crawl space system sits under the vapor barrier, not through the slab (there is no slab).

1. Choose a central location — typically near the fan's pipe exit point
2. Cut a 4" hole in the vapor barrier
3. Install a T-fitting or dedicated suction cup device designed for sub-membrane use, sealing the perimeter of the fitting to the vapor barrier with tape
4. Connect PVC pipe from the suction point, routing out through a wall or up through the floor to the fan

Step 4 — Fan, Pipe, and Sealing

Follow the same pipe routing, fan installation, and sealing steps as the slab procedure above. Key differences:

• Fan draws from the sub-membrane space, not sub-slab gravel
• Pipe exits through the rim joist or a drilled wall penetration — seal around the pipe exit thoroughly with spray foam or hydraulic cement
• All floor penetrations above (in the living space) should still be sealed for belt-and-suspenders performance

Step 5 — Test

Same as slab: 24-hour immediate test, 30-day follow-up. Sub-membrane depressurization in crawl spaces typically achieves significant reductions, but starting levels can be high — confirm with testing.

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Pro Tips from Certified Mitigators

Label your system. Tape a note to the fan or pipe with the installation date, pre-mitigation radon level, post-mitigation radon level, and fan model. Future owners and contractors will thank you.

Take photos before closing walls. Document where the pipe runs before any drywall or insulation goes back up.

Don't install the fan in living space. Fan noise and the risk of a quiet failure make living space mounting a bad idea. Attic or exterior only.

Check the manometer monthly. It takes 3 seconds. If the liquid levels are equal, your fan has failed — radon may be rising.

Interior pipe routing is better than exterior. Pipe inside the thermal envelope (through closets, interior walls, or the attic) protects the fan from UV, freezing, and animals. Exterior pipe works fine but shortens fan life in harsh climates.

Over-size the pipe, don't under-size. Use 3" pipe for standard installs; 4" if your contractor recommends it for high-flow needs. Narrower pipe increases system resistance and reduces airflow.

Don't forget the sump pit. An open sump pit in a basement is often the biggest single radon entry point. An airtight sump cover with a pipe knockout is a $65 fix that meaningfully improves system performance.

Retest every 2 years. Systems work for 5–15 years, but fans wear out. A periodic long-term test catches fan failures or changes in sub-slab conditions before levels creep back up.

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Common Mistakes to Avoid

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When to Stop and Call a Pro

DIY is great for straightforward jobs. Know when to call a certified mitigator:

• Radon above 15 pCi/L on initial test
• Multiple sub-slab zones with poor communication
• Block wall or stone foundation
• Post-mitigation levels still above 4.0 pCi/L after two suction points
• Crawl space with mold, standing water, or asbestos
• Any permit-required electrical work beyond your comfort level

A professional system costs $1,000–$2,500 for most slab homes and comes with a performance guarantee. The DIY savings ($700–$1,500 on average) are real — but not if the system doesn't perform.

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What to Buy

Everything you need is in our DIY equipment shop:

• [Short-term radon test kit](/shop) — start here before you order anything else
• [Standard DIY Mitigation Kit](/shop) — fan + fittings + manometer + warning device for slab homes under 8 pCi/L
• [Pro DIY Mitigation Kit](/shop) — higher-suction GX3 fan for 8–15 pCi/L or clay sub-slab
• [Vapor barriers](/shop) — 6 mil and 10 mil in multiple sizes for crawl space jobs
• [Core drill bit, hydraulic cement, sump cover, pipe hangers](/shop) — all the individual components

Not sure which kit is right for your home? Find a certified mitigator in your state — many offer free phone consultations even if you plan to DIY.