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Repair Off-Center Footings during Building Construction
It is sometime hard to position footings in the trench, so contractors often see walls that are not in the center of the footing (Figure 1). The foundation wall has to be located correctly to support the house, of course, so it has been placed off-center on the footing.
Figure 1: This incorrectly placed footing caused the foundation wall to be off-center. If the soil is very strong, this may not lead to problems. If the footing is on a weaker soil it is recommended that it is fixed.
In good bearing soil, it is not the matter of much concern about this foundation for the loads involved in a simple wood frame house. The full width of the footing is not needed to support the loads; wall can be constructed right on the edge of the footing and still have enough support. However, if it goes over the edge and have the wall sticking out past the footing on the side or on the end, then rotational force is generated which the footing is not designed to handle. In that case, an engineer has to get involved. If soils are relatively soft, the risk is even greater.
Figure 2: In strong soils, a mistake in footing layout can be corrected by placing gravel to support the wall (top).
In weaker soils, casting an augmented footing alongside the existing footing is recommended (above), connected by dowels epoxied into the side of the existing footing. Be sure to fill any notches in the footing, and cut off any existing steel dowels that will miss the wall.
In soils with high bearing capacity greater than about 4,000 psf, excavating next to the footing and under it and placing compacted large gravel into the space is suggested. That should be adequate to support the wall.
In weaker soils, the footing itself has to be augmented with steel and concrete. Excavation has to be done as before, but instead of filling it with gravel, drilling into the side of the footing has to be done and epoxy steel dowels into it, and then concrete is placed to extend the footing out to the proper width. 