Is partial underpinning an adequate approach to fixing sinkhole damage?
Other than denied claims for sinkhole damage (or “sink hole” depending on whom you ask), the most common question relates to how one fixes a sinkhole, whether it be in the yard or beneath the home.
When a sinkhole is fixed by partial underpinning
We spent the better part of a day this week on a case I believe worth writing about. A homeowner we represent in Ocala had a sinkhole “fixed” previously, by the use of grouting and underpinning. However, only part of the perimeter of the home was actually stabilized with underpinning.
Instead of underpinning the entire home, the insurance company’s engineer firm had instructed the insurance company to only authorize the use of six pins, to stabilize one-fourth of the home, where the damage was the worst.
Why partial underpinning doesn’t work
The easiest way to describe this cheaper approach to fixing a sinkhole would be to consider the structure of a dining room table. A table has four legs and a tabletop. The tabletop rests on the four legs, with the weight distributed evenly down the legs. If one of the legs is too short, the table will wobble. If one of the legs is missing then the table will likely fall.
The same principle applies to how to fix a sinkhole. The reason you use underpinning is that you are taking the weight of the home and removing the weight from the surface to a deeper area where the soil is stable. If you only pin portions of the home, you are now altering the weight of the home, with portions of it on the surface and the other weight being moved to the deeper soil material.
The problem is that now you have a two- or three-legged table, with areas moving, and others not. This tends to torque the house and cause other damage.
What engineers believe
We consulted multiple engineering firms – even some who work for insurance companies – and they all agreed that partial pinning was not the best approach to fixing this sinkhole. We presented these opinions to the Citizens Property Insurance Corporation representatives and hoped they listen.