Ever wonder how much it costs to dig a tunnel? Not just any tunnel—but one that runs beneath your home’s foundation, allowing for essential under-slab plumbing repairs. You’re probably looking for a clear answer on under-slab tunneling prices, and we’ve got you covered.
At Anchor Foundation Repair, we handle under-slab tunneling regularly, both as part of foundation repair projects and as a standalone service. While we have our own pricing, this article gives a general cost breakdown that applies across different companies.
We’ll go over what affects the cost of tunneling, what a typical project involves, and pricing estimates for small, medium, and large tunneling jobs.
Quick Refresher: What Is Under-Slab Tunneling?
Under-slab tunneling is a hassle-free way to access and fix plumbing leaks beneath your slab foundation. Instead of tearing up your floors and disrupting your daily life, workers create a tunnel from the outside, keeping all the mess and noise away from your living space.
The unpleasant alternative? Jackhammering through your floors can damage your foundation, make a mess, and force you to adjust your routine. While tunneling can sometimes be more expensive and time-consuming, many homeowners find it worthwhile for the convenience and minimal disruption.
Check out this comparison between tunneling vs. breaking through the slab for more info.
How Much Does Under-Slab Tunneling Cost?
Like most home repairs, tunneling costs depend on your unique situation. Typically, tunneling is priced per foot, making the total length of the tunnel the biggest cost factor.
Price Per Foot
Expect tunneling costs to range from $200 to $500 per foot, depending on the company and location. In some cases, plumbing companies may charge as much as $600 per foot (mostly because they would rather not do it).
Example Project Cost
For a standard hall bathroom with leaking drain lines, you might need 8 to 10 feet of tunneling. Using the price-per-foot range, this project could cost anywhere from $1,600 to $5,000.
To narrow it down further, typical pricing in the Bryan/College Station area runs between $3,000 and $4,900 for this type of typical job. Keep in mind—this only covers the tunneling. Plumbing repairs are billed separately by your plumber.
What Factors Affect Under-Slab Tunneling Costs?
While tunneling is mainly priced by the foot, several other factors can influence the final bill.
Starting the Tunnel
Starting a tunnel is one of the more challenging parts – but let’s face it, the whole tunneling process is hard. The initial hole to start a tunnel must reach below the perimeter beam of the home. They dig straight down as many feet as it takes and then dig straight up the other side of the beam to reach the underside of the slab. This allows for safe under-home work and prevents cave-ins.
There might be an extra charge to begin the tunnel due to the additional effort required at the start. That’s the way we do it, anyway.
More Leaks = Higher Costs
You may need additional tunnels or extensions if multiple leaks are found, increasing the total footage and cost. Sometimes, more leaks are only discovered after the initial repair, requiring further excavation.
Adjusting the Tunnel’s Starting Point
Obstacles like sidewalks, trees, or air conditioning units may require workers to begin tunneling further from the home, adding more feet (and cost) to the job.
Concrete Chipping
Even with tunneling, some plumbing lines may be encased in concrete, requiring additional work to break through. This adds labor costs, whether done by the tunneling crew or your plumber.
Backfilling & Mud-Pumping
After repairs are completed, tunnels must be properly refilled to prevent foundation issues. This process includes:
- Backfilling: Using a mix of excavated dirt and new topsoil.
- Mud-Pumping: Injecting a slurry of topsoil, water, and Portland cement to stabilize the foundation and prevent future shifting. This may or may not be part of the package depending on the company you choose.
In our book, mud-pumping is the best way to support a filled-in tunnel fully. Mud-pumping may be included in the per-foot pricing or listed as a separate charge.
Cost Estimates for Small, Medium & Large Tunneling Jobs
Beyond the standard hall bathroom example we offered above, here’s what you can reasonably expect for different typical project sizes:
- Small Project (4 feet or less): Around $2,500 or less, ideal for leaks near an exterior wall (e.g., kitchen sink, toilet, or tub).
- Medium Project (8 to 15 feet): Ranging from $4,000 to $7,500, typically covering multiple fixtures in one area (e.g., sink, toilet, and shower in a bathroom).
- Large Project (30+ feet): Costs can exceed $12,000 to $15,000, often required for full drain system replacements due to aging or damaged pipes.
We’ve also done some much larger homes and businesses needing extensive drain line repairs. These out-of-the-ordinary mega-projects required nearly 100 feet or more of tunnel. Tunneling costs keep going up when these longer tunnel lengths are needed. Again, these costs only reflect the tunneling and any backfilling. Plumbing repairs are an additional expense.
A small bit of good news is that *sometimes* homeowner’s insurance can cover the cost of under-slab tunneling in the right circumstances. So check your policy or talk to your insurance agent to see.
Ready for an Under-Slab Tunneling Quote?
While we don’t handle plumbing repairs ourselves, we can recommend local trusted plumbing professionals who understand our process and prioritize minimally invasive solutions.
At Anchor Foundation Repair, we specialize in expert under-slab tunneling, whether as part of a foundation repair or a standalone service for plumbing access. Our basic rate is $650 to start an under-slab tunnel, and $400 per foot after that (price per foot goes up after 20 feet) and we always mud-pump our tunnels to maximize support and minimize opportunities for foundation settlement.
Does tunneling sound like the right solution for your plumbing repair? The only way to know for sure how much your under-slab tunneling project will cost is to get a quote. Contact us online 24/7 to begin the FREE quoting process for tunneling, and let’s get started!
