Pasadena Solid Foundation Repair reaches problems under the slab for homeowners across Pasadena, TX. Sometimes the problem is under your house, and the only way to fix it is to get under your house. Breaking out the floor is one way to do that. Tunneling is another. It means digging a narrow passage below the slab so repairs can happen while the floor above stays intact.
This post explains what under-slab tunneling is, the situations where it is useful, how the process works, and what to weigh before you choose it. For a description of the work we do, see our under-slab tunneling service.
The basic idea
A slab on grade sits directly on the ground. If something below it needs attention, such as a pipe, a void, or the soil itself, you can either cut through the slab or go underneath it. Tunneling takes the second route. Crews dig a small access pit outside the house, then excavate horizontally under the foundation edge and along the path they need to reach.
Tunnels are kept as small as the job allows. Some are just wide enough for a person to crawl in with tools. Others are a little bigger to allow for equipment or supports.
Situations where tunneling is used
Repairing plumbing under the slab
Drain and supply lines run below many slabs. When one leaks or backs up, the leak can soak the soil and cause settlement. Tunneling can give access to the pipe so the line can be fixed or swapped out, in some cases without cutting a long trench through the living space.
Filling and supporting voids
Water can wash soil out from under a slab and leave an empty pocket. Reaching that pocket from below allows the crew to inspect it and place fill or support where it is needed.
Placing foundation support in hard to reach spots
If a repair calls for piers or beams in the middle of a house, reaching those locations from outside the wall can be impossible. A tunnel brings the work to the interior of the footprint. You can read more about deep support in our post on foundation repair methods.
Installing drains or moisture control below the floor
A drain line under the slab, or a barrier to control moisture, may be added when groundwater or leaks keep the soil wet. Tunneling avoids ripping up finished flooring to lay them.
Tunneling compared with breaking the slab
Both approaches have a place. The choice hinges on how big the job and how much of the floor is in the way.
- Tunneling leaves most of the floor untouched, so tile, wood, and cabinets stay in place
- Breaking the slab gives direct access and can be simpler for a short pipe run near the surface
- Tunneling produces less dust and noise inside the home
- Slab breakout can be less costly for a small area, but repairs to finish flooring add up
- Long or deep repairs are often easier to handle from a tunnel than from a trench
Neither one is always better. We look at the layout of your home, the depth of the repair, and the finishes above before recommending a path.
How the process works
- Locate the target. We use plans, pipe locating tools, and inspection to pin down where the work needs to happen.
- Dig the access pit. A pit is excavated outside the foundation, often at a spot that is easy to restore afterward.
- Advance the tunnel. The passage is dug under the footing in stages, with supports placed where the soil needs them.
- Do the work. Pipes are repaired, voids are filled, or supports are placed, depending on the plan.
- Backfill and compact. The tunnel is filled in layers and tamped so the ground is stable again.
- Restore the surface. The access pit is closed and the yard is repaired.
Because the passage runs under a loaded foundation, the crew works carefully and shores the soil as they go. Safety and stability drive the pace.
What tunneling cannot do
It is not a fix by itself. Tunneling is a way to reach the problem, not a cure for the problem. If the slab has settled, the piers or fill placed through the tunnel are what restore support. If a pipe leaks, the repair to the pipe is what stops the water.
It also is not suitable for every site. Very loose or wet soil, or a very shallow footing, can make a tunnel unsafe. In those cases another approach, such as breaking through the slab in a limited area, may be recommended.
Signs you may need it
A few symptoms point toward trouble below the floor:
- A wet spot or warm spot on the floor with no visible source
- Water noises in the walls or floor when no fixture is in use
- A water bill that jumps without a change in use
- A hollow sound when you tap a section of the slab
- Cracks that follow a line where a pipe runs beneath the concrete
A leak detection test and a floor elevation survey can tell you whether the trouble is under the slab and how far it goes.
Questions to ask any contractor
- How will you get to the work area, and where will the access pit go?
- How will the soil be supported while the tunnel is open?
- What will be done to compact and restore the ground afterward?
- Will my slab be checked for cracking or movement during the project?
- What happens if you find more damage than expected?
What affects the scope and price
Two tunnels of the same length can be very different jobs. A few factors change the scope of work more than anything else.
- Depth of the target, since deeper work needs more shoring and more soil to move
- Soil type and moisture, because wet or loose ground needs more support
- Distance from the access pit, which sets how long the tunnel has to be
- Whether utilities such as gas, water, or electric lines cross the path
- Access to the yard and where the removed soil can be stored
We explain these factors when we walk the property, so the estimate you receive matches the work that is actually needed. If you are also concerned about long term movement, our article on why concrete cracks and sinks covers how water below a slab can affect other paved areas on your lot.
Common questions
Will tunneling damage my floor?
The slab stays in place, so the floor above is not removed. Crews take care not to disturb the soil under the concrete beyond what is needed.
Is tunneling only for leaks?
No. It is also used for void repair, foundation support, and drainage work below the slab.
How long does a tunneling job take?
Timing follows the tunnel length and the kind of repair. Small jobs may take a few days. Larger ones can take longer, and we give a schedule after evaluating the site.
Can I stay in the house?
Most homeowners stay home. The work is mostly outdoors and below the floor.
The bottom line
Under-slab tunneling lets a crew get at the soil below your home while the floor stays put. It is useful for pipe repair, void repair, and foundation support when the work must happen inside the footprint. If you suspect a problem below your slab, start with an inspection so the best method can be chosen.
We help homeowners in La Porte, South Houston, and Galena Park and nearby. If this sounds like your situation, see our foundation underpinning, slab foundation repair, and concrete slab repair pages. For outside information, EPA WaterSense has tips for finding and fixing household water leaks.
Call +17139292237 to talk about what is under your floor.
