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Foundation Repair – Disadvantages of Drilled Bell Concrete Piers

February 8, 2010

in Foundation Repair, Foundation Repair Methods

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Drilled Bell concrete pier image

Drilled bell concrete piers are a common method of foundation repair, but are actually best suited for newly constructed homes and structures. The installation of bell bottom piers in previously existing structures presents a myriad of problems.

Installing Drilled Bell Piers

First, let’s take a look at how Drilled Bell piers are installed in a house. Shafts are dug diagonally underneath a home’s foundation from the exterior of the structure. Once they reach the appropriate depth, either stable soil or bedrock, the bottom of the shaft is widened using special bits to create a bell shaped “foot”. The shaft is often reinforced with steel rebar before concrete is poured into it (further reading). Once the shaft is filled with concrete, the concrete must cure for 1-2 weeks. Upon completion of curing, the house is lifted and placed on top of the Drilled Bell piers.

The numerous Disadvantages of this Method as it Relates to Foundation Repair:

  1. First, an enormous amount of excavation is required and the excavated soil must be redistributed somewhere.
  2. In order to drill underneath the house heavy equipment will be placed next to the home causing considerable disturbance to adjacent landscaping.
  3. Also the vibrations of the drills, depending on their intensity, can cause foundations to crack further.
  4. Water may seep into the shafts before the concrete is poured causing the bell foot (the support) to be compromised. Any water seepage must be addressed before the concrete can be poured.
  5. The presence of toxic or flammable gasses may prevent thorough inspection of the shafts (book: Design of Foundation Systems).
  6. Upon curing of the concrete, pressure is applied, usually using bottle jacks, to the outter edges of the foundation to lift the structure up onto the piers.
  7. It is not possible to install interior bell piers on existing structures.
  8. The process takes 2-3 weeks before it is completed

So it is easy to see that drilled bell concrete piers installed in existing structures are not a viable option of foundation repair. If your home or business was built on top of belled piers, you will have adequate support.

Steel Piers compared to Drilled Bell Piers

In comparison, Superior’s Steel Pier foundation leveling process requires minimal excavation, no curing time for concrete, the installation usually lasts no longer than 3 days, can be installed in the interior of the house, does not depend on soil for support, and causes minimal disturbance to landscaping around the house. Because our steel piers reach all the way to solid bedrock, your home is protected against the effects of expanisve soils prevalent in our area of Central Texas, thus effectively counteracting the most common cause of foundation problems in our area.

Further Reading on Drilled Bell Concrete Piers:

myfoundationrepair.com
foundationdoctor.info
theconstructor.org