The Pressed Piling with Insert method of foundation repair was developed in the 1980s in an effort to eliminate one of the major disadvantages with its predecessor, the pressed piling method. The primary driving force behind the development of these methods was the desire to raise the profit margins of the foundation repair companies by lowering the installation costs. Unfortunately, the pressed piling with insert method of foundation repair is a flawed method and rarely provides the commercial or residential property owner with a long term solution.
Pressed piling with insert was preceded by pressed piling. Prior to both of these methods the accepted and widely used method was the poured concrete with steel rebar method, also known as the Bell Bottom Pier method. This was, and still is, a proven and time tested method but it requires higher material costs for more concrete and steel and higher labor costs. It also took / takes weeks to complete rather than days. Therefore, the pressed piling and pressed piling with insert methods were born. They significantly cut material and labor costs as well as the time required on the job. They are both very profitable methods for the repair contractor.
The first major disadvantage of the pressed piling with insert method of foundation repair is that it relies on the weight of the home or building structure to force concrete cylinders (piles) into the ground. It requires a great deal of force to push a cylinder of concrete that measure six inches in diameter and twelve inches in length into the ground. It requires a far greater force to push this concrete cylinder ten, fifteen or twenty feet into the ground. During this process of forcing concrete cylinders into the ground a “refusal point” will be reached. At this point the work crew should stop immediately. The weight of the home or building will NOT push the cylinders any further into the ground. The limit or refusal point has been attained. If the work crew continues their attempts to force concrete cylinders past the refusal point they will fail. What they will do is raise a portion of the home or building foundation into the air. At this point they could serious damage to the foundation they are trying to repair.
The second major disadvantage of the pressed piling with insert method of foundation repair is that the column of cylinders being pushed into the ground can become misaligned. The goal is to have a vertical column of cylinders under a portion of the foundation to provide support. If the column becomes misaligned then it offers little or no support for the foundation. This was and still is a major problem with pressed pilings. To address this problem the concrete piles were manufactured with a hole in the center to allow a steel rod or cable to be inserted. But this approach has its own set of problems. If the concrete cylinders are not perfectly aligned then it is impossible to thread a steel rod to the bottom most cylinder. Other contractors attempted to “snake” a cable through the concrete cylinders and therefore “string” them together. But the cable was never given any tension, either during or after the installation and therefore it offers little or no help in resisting the forces of soil movement. There is no method to guarantee the cylinders are not “wandering” off at an angle. Neither the steel rod nor the cable will prevent misalignment. In addition, cables are pre cut to specific lengths and if the concrete pilings need to be driven to a deeper depth then the cables are too short.
Typically no soil test is performed when the pressed piling with insert method is used. If no soil test is performed then the repair contractor has no idea of the depth of stable soil or bedrock. It then becomes a “game of luck” for the home owner or building owner. The property owner or homeowner will be lucky if the weight of his/her home or building is sufficient to push the columns of concrete pilings into stable soil or bedrock. If the weight of the home or the building is insufficient to push the columns of concrete pilings into stable soil or bedrock then he or she will be unlucky. Without a soil sample the entire foundation repair process is a gamble with this method.
An added disadvantage with the pressed piling with insert method is that the holes in the concrete cylinders introduce a pathway for water. The water will seep down the hole and into the soil surrounding the cylinders and expand. Then the water will evaporate and the soil will shrink. This process will be repeated many times and exert horizontal and vertical forces on the column of concrete cylinders. The water will also reach the bottom of the column and further “pack and consolidate” the soil underneath the column. All of these forces will contribute to the early failure of this method.
Author Resource:
Martin Dawson is the co-founder (1984) of Dawson Foundation Repair. He is a leading authority in Texas and other southern states on repairing failed commercial and home foundations using the thoroughly researched drilled Bell Bottom Pier method. http://www.DawsonFoundationRepair.com/
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