Foundation Repair Methods

Pressed Concrete Piers

This method utilizes concrete cylinders that are approximately 12 inches long by 6 inches in diameter. There are two basic types of cylinders, some are solid and some have holes through the centers from end to end.

There are companies that claim that placing various materials in the center holes makes the piers more effective. They have even patented the process of placing different materials in the core of the piers to gain a marketing advantage.

Others point out that leaving a void at the core of the pier weakens it making in susceptible to crushing under the weight that is used to press it into the ground. The bottom line is that there are structures that are supported by hollow and solid concrete piers that are lasting and performing equally well.

Installation consists of digging holes next to the foundation in the areas where piers are required to allow access directly beneath the foundation. A hydraulic press is then used to press concrete cylinders into the soil directly beneath the foundation using the full weight of the foundation and the structure it supports.

The cylinders are pressed one on top of the next until they refuse to move any further. This process is continued until all piers are installed. Next the foundation is raised simultaneously in multiple locations and a cap and shims are placed on top of each pier and then the weight of the foundation is allowed to rest on the piers.

Pressed concrete piers are effective in almost every situation because they do not depend on reaching bedrock, instead they are supported by skin friction. That is the friction between the surface of all cylinders and the soil that surrounds them.

Imagine that you are holding a rope tied to a heavy weight. You can lift a limited amount of weight by gripping the rope with your hands. You are creating skin friction between the rope and your hands. If you have a friend to help you can probably lift twice as much. What if you have 5 or even 10 or 20 friends to help?

This method is very effective because the weight of the structure is carried by multiple piers with each pier supporting only a fraction of the weight that was used to press it into the ground.

Advantages

  • Effective in almost every situation
  • Relative inexpensive
  • Quick installation typically 1 to 3 days
  • Durability - Outlasts all other materials

Disadvantages

  • Holes must be dug.
  • Shrubs may need to be removed.

This is the preferred method of foundation repair by most major foundation repair companies. The disadvantages mentioned above are really not a problem if you choose a reputable contractor who does proper cleanup and saves and replaces all shrubbery.

Bell Bottom Concrete Piers

This method uses a drilling system to drill a hole with a flared bottom. This hole is then filled with steel reinforced concrete. The concrete is allowed to cure for two weeks or more and before the weight of the foundation can be supported. This method is also used in new construction to provide support of a foundation before it is poured.

Advantages

  • Can be installed before foundation is poured.
  • Durability - Outlasts all other materials.

Disadvantages

  • Cost
  • Holes must be dug.
  • Shrubs must be removed
  • Repairs can take up to 3 weeks.
  • Limited depth.

Pressed Steel Peers

This method utilizes steel segments that are pressed one by one to the point of refusal. With pressed steel piers the foundation is typically supported with a bracket that is bolted to the outside of the foundation.

This method is most effective in areas where bedrock can be easily reached. In areas where there is no bedrock this method is rarely used.

Advantages

  • Cost
  • Quick Installation
  • No holes to dig.

Disadvantages

  • Effectiveness limited to certain regions
  • Durability - metal does not last as long as concrete

Helical Steel Piers

This method utilizes a steel auger that is twisted into the ground. It also is usually bolted to the outside of the foundation to provide support.

Advantages

  • Quick Installation
  • No holes to dig.

Disadvantages

  • Cost
  • Durability

This method is fast but it may not be as durable as other methods that use concrete piers and support is provide by the auger at the very bottom of the pier.

This method can work well for new construction however since the depth that this type of pier can reach is limited it's effectiveness is also limited to only those situations where it's reach is below the soils causing the problem. It is also somewhat expensive as compared to other methods.

Slab Jacking or Mud Jacking

This method utilizes a high pressure pump to inject liquid material under a slab in order to raise it in areas where it has sagged. Common materials are concrete, a special mud mixture and polyurethane products.

Advantages

  • Quick Installation
  • Cost

Disadvantages

  • Not a complete solution

Mud Jacking is best suited for use in conjunction with one of the other methods mentioned above to provide support for internal areas where the slab has sagged.

While this method can be used as the primary means of repair it's effectiveness can be short lived. In fact it can cause additional damage because if it is used to raise the foundation in an area where the soil is very dry and the soil becomes wet it can expand and raise the foundation to the point of damaging the structure that rests upon it.

If you think you have a foundation problem, you should contact a foundation repair specialist for an evaluation. Many companies provide a free inspection and estimate of the cost to repair.