Know the facts before deciding on tunneling under a house versus cutting concrete slabs.
Which should homeowners choose – tunneling under or cutting concrete slabs? When you have under-slab plumbing leaks or foundation repairs, this is important. Is it better to tunnel under a house, or is cutting through the concrete slab the best way to go?
The web is full of questions on what to do when there are under-slab plumbing issues or needed foundation repairs. Should you tunnel under the slab or cut into the slab. Some are tunnel-only advocates, while others push the slab-cutting alternative. No one size fits all. Each repair situation is different and needs to be evaluated on its own.
Before committing to one method, understand the differences. Separate fact and fiction about the two different methods.
Tunneling Cost
Myth: Tunneling under a house is always more expensive than cutting concrete slabs.
Fact: After considering all costs, consider the often cheaper option, tunneling. Breaking through a slab involves:
- Removing and replacing flooring
- Home interior cleaning after the repairs.
- Jobs requiring vacating the home while work is in progress
Tunneling generally costs more for situations where the floor finishes are inexpensive. For homes with high-end finishes, tunneling can cost less. For the average homeowner, tunneling will cost more. Advanced prefers tunneling under a foundation. The reason? It has distinct advantages over cutting concrete slabs:
- Homeowners can stay in their homes during the repairs.
- Avoids indoor mess and disruption, especially when having to replace large
- Sections of flooring or needing to install many foundation piers/pilings.
- For plumbing, plumbers don’t have to pinpoint the exact location of the leak.
One Size Does Not Fit All
Myth: Cutting concrete slabs is a one-size-fits-all solution.
Fact: Different types of slab foundations need different kinds of repairs. Avoid breaking through structurally suspended flat slabs. Flat slabs have no interior beams.
Strength After Repair
Myth: Cutting through concrete slabs and then applying patches leaves slabs less secure.
Fact: If re-poured the right way, patches are secure. In 21 years, I remember only one interior patch fail, including patches in garages that cars drive on.
DIY
Myth: You can do the tunneling yourself using a tunnel boring machine.
Fact: Tunnel boring machines bore tunnels, generally for mining. Their large size and cost prohibit use in homes. Use machines capable of boring small-diameter tunnels. Small tunnels are used for threading through pipes, electrical lines, and other small-diameter items. Tunneling is challenging, to say the least. I would not recommend that a homeowner try it. One homeowner that I know of tunneled. It took 6 months to do what we do in a week.
Mudjacking
Myth: Mudjacking is an excellent way to fill voids created when refilling a tunnel.
Fact: Mudjacking requires specialized equipment. I recommend people not use mud jacking when expansive soils heave. Using mud jacking in such situations can lead to future movement. For plumbing repairs, Arch recommends avoiding mud jacking. The pumped-out material surrounds the pipes and then hardens. If the underlying soils shrink during a dry period, the soils will shrink and go down. When the soils shift down, the concrete surrounding the pipes settles, pulling the pipes down and breaking them.
Soil compaction Tests
Myth: A soil compaction test is required to prevent voids after tunneling.
Fact: When moving soils, engineers prefer compacting the soil to prevent it from settling later. A compaction test is a lab test. Tests often have a specification of 90 or 95% of Proctor Density or modified Proctor Density. It is necessary to use mechanical compactors to reach the specified density. These compactors will not fit in tunnels. Voids occur after refilling tunnels. Voids are okay, as slabs can span over empty spaces. Long tunnels get drained and sealed.
Insurance
Myth: Insurance companies prefer tunneling.
Fact Insurance companies prefer the solution that costs the least.
So What Next?
Does your home show signs of foundation problems? What kind of foundation repair method meets your needs? We are happy to help you get your home back into tip-top shape. Give us a call at 214-467-9700 or get a free quote today!
