Think Underpinning is Better than Compaction Grouting? Think Again…

Recently, an article published in the Ocala Star-Banner suggested that underpinning was a far more effective way to repair sinkhole damage than compaction grouting. From the author’s perspective, grouting alone is completely ineffective. Sinkhole damage, repaired through the use of underpinning will ensure that the house, “will never move again.” The author went on to say that grouting causes a myriad of environmental problems, such as negative impacts on water tables and damage to “surrounding homes and our overall environment.” Additionally, the author, stated that compaction grouting is costly and underpinning is “cheap” by comparison. Perhaps, his boldest statements were these, “I’ve never seen an underpin job fail,” and “I now refuse to grout a home without also underpinning. And I do it for free.”

underpinning

These ill-conceived statements can potentially cause a great deal of confusion for a homeowner who is facing sinkhole damage on his or her property. Those of us outside of the industry know only what we are told by people whom we believe to be the “experts.” Additionally, before I met Ralph Meder, geologist at MCD of Central Florida, I, too, had my own misguided ideas about the different repair options. I remember asking him directly if underpinning was more effective than compaction grouting because, from my perspective, it seemed like the answer would be “Yes, it is.” I was wrong.

First and foremost, the only people qualified to determine what type of sinkhole repair will be the most effective, are geologists and licensed engineers. A contractor, no matter how knowledgeable, does not have the background, education, or experience to talk about the benefits or detriments of one sinkhole repair option over another. What it boils down to is this — compaction grouting and underpinning are both effective techniques. The type of sinkhole is the determining factor that geologists and engineers use to recommend the appropriate repair option. All sinkhole repairs are performed under the supervision of a licensed engineer or geologist. Furthermore, when not done correctly, both underpinning and compaction grouting can fail. Yes, it’s just as I said, “Underpinning can and does fail.”

Ralph Meder told me about an investigation he did in Safety Harbor, “…the house had been underpinned only. The cracks were repaired, painted, and the house was sold quickly to a young couple who were clueless that a sinkhole had been found. My investigation revealed that the underpins were “popping up” from their locations through the pool deck, lanai slab, driveway slab, and the front entry. Significant cracking and structural damage was observed. As a matter of fact, the house was only “partially underpinned” as per the “engineer’s plan.” I use that term loosely, because the “engineer,” (who signed the report), was not an active licensed professional engineer. Furthermore, the original sinkhole condition was never addressed and the problem was never solved until we grouted the house. 

My point is, if they grouted the house to fill the solution cavity which was located directly below the house, underpinning was not necessary. The upper 10 to 15 feet of soils, which are considered the “zone of influence” supporting the foundation, were loose to medium dense. The house was both deep and shallow grouted, and the helical piers were replaced around the entire structure to re-level and support the structure. Was it expensive? Oh yes. But the insurance company went after the original remediation company to recoup the cost. That’s another story. In my professional opinion, you have to consider the geology first and foremost, and base your remediation methods on the geologic conditions. Communication between the geologist and engineer is crucial to provide the client with the best method or methods to solve the problem!”

Ralph Meder also talked about the article’s charge of environmental damage caused by compaction grouting. “In my experience, I’ve seen grout affecting pool shells (lift), damaged septic drain fields (plugged percolation zones), and neighboring properties (lift). It wasn’t the grout per se, but the soils that lift. These situations occurred due to poor monitoring or to poor remedial design. Proper pump rate and mix design is important. Environmental hazards typically do not occur. If the depths to limestone (where sinkholes form) is near the surface, say within 20 feet, “deep grouting” quantities are limited and are followed by shallow, chemical grouting. The compaction grouting is a low-slump, low-mobility, viscous material; therefore, it doesn’t travel far creating large environmental impacts such as contaminated groundwater, damaged wetland ecosystems, and so on. It doesn’t flow or wash away, unless the slump is too low. The monitor performs slump tests to make sure the grout is per specifications. Ultimately, environmental damage is caused by poor design and monitoring.”

If you are a homeowner, beware of grandstanding! Contractors who say that they will provide a repair for “free” may be violating the law. Sinkhole repair is a costly proposition no matter what the circumstance. The costs of underpinning can be equivalent to the costs of compaction grouting when done correctly. “Free” takes on a whole new meaning in that case. Free means that costs must be cut somewhere else to mitigate the costs of underpinning. Finally, consider that the author — Taylor Yarkosky of Advanced Pier Technology (also known as “The Sinkhole Guy,”) — has possibly been linked to sinkhole fraud as per allegations made in a Tampa Bay Times article in January of 2012.

If you have a confirmed sinkhole on your property, make sure you know what to look for when selecting a sinkhole remediation company. 

As a recognized leader in sinkhole remediation and with over a decade of experience, Helicon has completed thousands of successful projects.

At Helicon, we keep our promises. For more information, please call us today at 813-567-1065