Support is installed down to ground that will carry the house, the weight of the structure is transferred onto it, and the house is raised toward its original elevation as far as it will safely go.

How deep support has to reach under Chicago

Support has to bear on ground that will carry the house. The dominant mapped soil here is Orthents, clayey, nearly level, and the fastest of the largest mapped soils takes water in at 0.4 inches an hour, so what lies under one house is not what lies under the next. Depth is established during installation — by pressing a pier until it carries the load it was set for, or by turning one to a target torque — which is what makes it the single largest unknown in any quote written beforehand.

The reasoning behind that

It starts with the survey, because the pier count and their locations come from where the structure has moved rather than from a rule. Skipping this step is how a house gets somebody’s standard scope. Then access. Perimeter points are excavated from outside down to the footing; points inside mean working from the basement floor. Support is pressed or turned down to competent ground — push piers are driven using the weight of the house itself, helical piers are turned until the torque reaches a target that stands for the load. Then the transfer and the lift. Jacks take the load onto the new support and the structure is raised in small increments across several points at once, watched for how the building responds. This is where the judgment sits: how far to go is decided by the house, not by the survey. Finally backfill, patching, and — where it was in the scope — the plumbing test. The drainage work that keeps water off the walls is a separate operation and is commonly a separate quote, which is why it is commonly not done.

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