How Long Does Radon Mitigation Take? (Timeline Explained)

One of the most common questions homeowners have before scheduling mitigation is: how disruptive is this going to be? The short answer — most installations are completed in a single day and require minimal preparation on your part.

The Installation Day: 3 to 5 Hours

A standard sub-slab depressurization (SSD) system typically takes 3 to 5 hours from start to finish. Crawl space systems with sub-membrane depressurization (SMD) can take longer — anywhere from 4 to 8 hours — because the vapor barrier installation is more labor-intensive.

During that window, the contractor will:

1. Inspect the foundation — identifying the best suction point location, checking for visible cracks, and confirming adequate sub-slab communication with a pressure diagnostic.
2. Core-drill through the slab — usually a 4-inch hole at the selected suction point. This takes 15 to 30 minutes.
3. Install the pipe and fan — running PVC piping from the suction point to the exterior, typically exiting through a basement wall or garage before routing above the roofline.
4. Seal visible openings — caulking cracks and sealing visible gaps in the foundation floor and walls to improve system efficiency.
5. Electrical connection — hardwiring or plugging in the inline fan, which runs continuously at low wattage.
6. System verification — confirming negative pressure at the suction point with a manometer or smoke test.

When Do Radon Levels Drop?

The mitigation fan begins pulling radon from beneath the slab the moment it’s turned on. Most homeowners see a significant drop within 24 to 48 hours. Full stabilization typically takes a few days as the system reaches equilibrium under the slab.

Post-Mitigation Testing: When and How

You should wait at least 24 hours after installation before starting a post-mitigation test. A short-term test (48 to 96 hours) is the most common follow-up. Your contractor may leave a test kit behind, or you can purchase one separately.

The goal: confirm levels are below 2 pCi/L, which is achievable in most homes with a properly installed system. If post-mitigation levels are still above 4 pCi/L, contact your contractor — additional suction points or a higher-capacity fan may be needed.

What You Need to Do Before Installation

Very little preparation is required. Keep the area around the planned suction point clear. If the pipe will run through a closet, move any stored items out of the way. The contractor handles everything else.

Real Estate Timelines

If mitigation is required as part of a home sale, the installation itself won’t delay closing. The 48-hour post-mitigation test adds a couple days, but experienced contractors are accustomed to working around real estate deadlines. Most can schedule and complete the full process — installation plus confirmatory test — within a week of booking.

Find certified radon mitigation contractors in your area to get a quote and confirm scheduling availability.