How To Look At A House
McGarry and Madsen's home inspection blog for buyers of
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Is it safe to buy a house with sinkhole foundation repair?
Wednesday, July 31, 2019
"In general, if a repair has been certified by a licensed engineer and completed to the satisfaction of the homeowner’s insurance company, it is likely safe,” according to the Florida Department of Environmental Protection. "However, since these are natural systems, there can be no guarantees that a repaired sinkhole will not cause future problems.” So while it is possible for further sinkhole development to cause problems with a house that has had foundation repair, it is unlikely. Here’s two reasons:
- The foundation is “pinned,” which means that steel rods are driven into the ground next to the wall around the perimeter of the home until “refusal” at solid rock, then a bracket several feet long is attached to the rod and fitted under the foundation (as shown below) and tightened, to provide support.
- Concrete grouting under the floor slab is also part of the specifications for virtually all sinkhole foundation repairs. This fills voids under the center of the home and, again, only very significant collapse (not minor settling) of the soil under the home would cause a new problem.
But how possible is it, really? We asked Michael Driscoll, a structural engineer that specifies 300 or more foundation repairs a year, and he could only think of one repair that had further problems. It was for a homeowner that dismissed the contractor before the work was complete. But an engineer cannot predict with certainty that the house will not have problems in the future if the underlying condition that caused the original settlement progresses further.
So it’s important to verify that all the work specified in the engineering report was really done. Pinning without grouting under the slab, for example, can lead to problems later. And there was a re-collapse of a sinkhole under a repaired home in 2017 near Tampa, Florida, for exactly that reason. Although the engineer recommended grouting, which is the only way to actually fix the ground under a home, the homeowners decided to only have pins installed. This stabilized the house, but did not fix the underlying problem, and the expanding sinkhole eventually overhelmed the pins. Plus, the second time around it took down a neighbor's home too.
So you should get a copy of the engineer’s report, but also talk with the foundation company that did the repair. They are usually happy to review the details of their work with you. We did an inspection several years ago of a repaired sinkhole house in Gainesville, Florida, where the seller gave us a copy of their Property Disclosure Statement that included the foundation contractor’s detailed summary of the extensive foundation work done underground. Except that nothing was done except cosmetic stucco repair above ground. See our article Should I trust the Seller's Property Disclosure Statement? for details.
Also, we recommend reading our blog post Should I buy a house that has had foundation repair? for strategies to ensure you are getting an adequately repaired house. Also, see How does a repaired sink hole under a house affect its market value?
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