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Tunneling Under a House vs Cutting Concrete Slabs 7 Myths Dispelled

Know the facts before deciding on tunneling under a house vs cutting concrete slabs

Homeowners have choices when making decisions for under slab plumbing leak or foundation repairs. Is it better to tunnel under a house or is cutting through the concrete slab the best way to go?

How-to websites and blogs are full of questions on whether to tunnel under a house or cut slabs for plumbing and foundation repairs. Some are tunnel only advocates while others push the slab cutting alternative. There is no one size fits on regarding tunneling under a house or cutting through concrete slabs. Each repair situation is different and needs to be evaluated on its own.

Before committing to one method over another, understand the difference between fact and fiction regarding the two different methods.

Tunneling Cost

Tunneling under a houseMyth:  Tunneling under a house is always more expensive than cutting concrete slabs.

Fact:    After considering all costs, consider the often cheaper option, tunneling.  When breaking through a slab, remember the flooring with have to be removed and replaced, the interior of the home cleaned, and possibly homeowners will have to move out while work is in progress.  Tunneling generally costs more for situations where the floor finishes are inexpensive.  For expensively finished homes, tunneling can cost less.  For the average homeowner, tunneling will cost more.  Advanced prefers tunneling under a foundation because it has some 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 multiple foundation piers/pilings.

   *   For plumbing, plumbers don’t have to pinpoint the exact location of the leak.

 

Cutting concrete slabsOne Size Does Not Fit All

Myth:  Cutting concrete slabs is a one size fit all solution.

Fact:    Different types of slab foundations need different kinds of repairs. Aavoid breaking through structurally suspended flat slabs.  Flat slabs have no interior beams.

 

Cutting slabsStrength After Repair

Myth:  Concrete slabs are never quite as secure when patches are applied after cutting through them.

Fact:    If properly repoured, patches are secure.  In 21 years, I think that we have only had one interior patch fail, including patches in garages that cars drive on.

 

Tunnel under houseDIY

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 prohibits use in homes.  Use machines capable of boring small-diameter tunnels threading through pipes, electrical lines, and other small diameter items. Tunneling is physically 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 a good way to fill voids created when refilling tunnel.

Fact:   Mudjacking requires specialized equipment.  I strongly recommend that people not use mudjacking in any situation involving expansive soils that have heaved.  Using mudjacking in such situations can lead to future movement.  For plumbing repairs, Advanced recommends avoiding mudjacking.  The pumped out material surrounds the pipes and then hardens.  If the underlying soils shrink, say during a dry period, the soils will shrink and go down.  When the soils go down, the concrete surrounding the pipes will settle, pull the pipes down, and break them.

 

Soil compaction Tests

Myth:  Required soil compaction test prevent voids after tunneling.

Fact:    When moving soils, engineers prefer compacting soil, preventing later settling.  A compaction test is a lab test.  The tests usually have a specification of 90 or 95% of Proctor Density or modified Proctor Density.  To reach the specified density, it is necessary to use mechanical compactors which will not fit in tunnels. Voids occur after refilling tunnels.  Voids are okay, as the foundations are capable of spanning across the voids.   Long tunnels can be 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? Like to see what kind of foundation repair method meets your needs? We will be 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 online today!