This week I got a call from a person who had foundation problems. They didn’t just want a repair though. They wanted to know what was the cause of the foundation failure. The caller said that they were told that there had “been a pond under the house”, and wanted to know if that was the case. Now, this may sound strange, but in foundation repair engineering we don’t always know exactly what is causing the failure. Why is that? It’s because of cost. If you have a corner of your house that is settling, and cracks that are developing, the solution is usually to put in piers to support the foundation.
We can look around the house, probe the ground, and most of the time that tells us what the problem is. However, to determine exactly what is happening would require test borings, and possibly ground penetrating radar. You can end up with a $10,000 geotechnical investigation for what is a $3,000 repair. That’s not the most economical way to approach foundation repair engineering, and it’s not necessary.
What if there was a pond under this house? If we had failures under the entire house, a more thorough investigation would be justified. One house I investigated in particular we had to do this. The house was settling in a very odd way, basically everywhere in the structure. We cored into the concrete floor, and hand augered into the ground under the house. Several feet down we found a trash pit. We had to map this one out, and we took more borings around the house to see what was going on. The trash pit was everywhere. Unfortunately, we found that repairing the house would cost almost as much as the house was worth.
The builder attempted to salvage the structure with filling the trash pit with grout, which was not our recommdation ( we recommended demolition – there was no fix possible). Some months later the house continued to settle, and the builder did tear the house down. He called us, and we went over to see what was underneath the house, and it was a huge pit full of trees, stumps, and various other junk. There was no solution unfortunately, and the house had to come down. It was very expensive for the builder because his insurance didn’t cover it. He had no recourse with the developer, since the developer claimed the trash pit pre-dated his ownership of the property.
Generally, when we investigation a foundation failure, we don’t need to do an extensive investigation. There are exceptions, and it can be expensive if it gets to that point.
