Methods of Foundation Repair
Below is a comparison of the four major foundation repair methods in east Texas. While each has its advantages and its disadvantages, a side-by-side comparison of Dawson’s bell bottom Pier method clearly demonstrates that it is the best, safest, and most reliable way to solve a foundation problem. When you get the facts you can be confident in your decision to trust Dawson Foundation Repair.
If you would like a more technical examination of each of the methods of foundation repair, check out ADSC’s article Potential Heave in the Pressed Concrete & Pressed Steel Piles in Residential Foundation Construction which details serious problems with piling methods in the Dallas and Fort Worth areas and how they can damage your home’s foundation, or take a look at the conclusions of PhD recipient Tom Witherspoon made in Load Capacity Testing and Analysis of Residential Underpinning Systems in Expansive Clay Environment.
Bell Bottom Pier Method
At Dawson Foundation Repair, we have built a company and a reputation over the past 23 years by providing a long term solution for concerned homeowners. Our work is backed by our years of experience, a lifetime service agreement, and our satisfied customers. We know the bell bottom pier method is superior to all other methods because we install it every single day and have seen it perform time and time again.
The bell bottom pier method is the only thoroughly researched slab repair method on the market today. This pier design – poured concrete reinforced with steel rebar – is the same conceptual pier design used in the construction of commercial multi-story buildings and highway overpasses. They can be installed in any of the soil and moisture conditions found in Texas and cope equally well from Dallas to Corpus Christi, Beaumont to Austin.
Click here to see a bell bottom pier up close
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Advantages
| ♦ | The bell bottom pier method is a thoroughly researched and proven foundation slab repair method. University of Texas load test data is available for Houston area soil. (Report No. 09-11F) |
| ♦ | Your soil is tested on site down to 15-18 feet deep for strength and condition. |
| ♦ | The size of bell and depth of shaft will be custom designed for your house and will be between eight and fifteen feet deep depending on the depth of stable soil and other factors such as the presence of water, sand, or rocks. |
| ♦ | The shape, size, and depth of bell and the angle of the shaft can be inspected. |
| ♦ | Two layers of steel rebar are placed in the cap or upper portion of the pier. |
| ♦ | High strength concrete is ordered from the plant for each house. |
| ♦ | Three 1/2" steel rebars are installed in the center shaft. |
| ♦ | Large bell bottom piers give solid support for your home's slab. |
| ♦ | Bell bottom piers anchor against uplift. |
| ♦ | Safety factors are designed into each pier. |
| ♦ | There are no damaging forces exerted on your house during installation. |
| ♦ | The homeowner can move heavy items in the house and add new ones without concern for the foundation. |
Disadvantages
| ♦ | There is an approximate two week waiting time required to allow the concrete to dry and gain full strength. |
| ♦ | Improper construction will affect performance. |
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Pressed Piling Method
Concrete pressed pilings are installed all over Texas, but are particularly popular in places with soft, clay rich soil such as Corpus Christi, Houston, and Beaumont. Pressed pilings are composed of a series of precast concrete cylinders which are installed by digging a hole under the house and then, by using the weight of the home as the driving force, the cylinders are driven into the ground. This method has two major drawbacks: the cylinders are not secured together in any way and the slab itself is used in the driving process.
Because the cylinders are not secured, they cannot and will not resist horizontal movement, they can easily be set at an incorrect angle, and pilings can crack without being noticed during installation. Because the slab is used in the driving process there is no way to tell how deep the pilings will end up being driven. This means that the pilings could reach a point of refusal (the point at which they can go no deeper into the ground) which is not properly anchored in stable soil. If not in stable soil, the pilings provide no benefit, but if an installation crew forces the cylinders beyond this point, they can crack the slab and cause major damage to the home.
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Advantages
| ♦ | There is no waiting for the concrete to cure. |
| ♦ | The total job time is short. |
Disadvantages
| ♦ | It is an unproven repair method. There are no capacity tests in Texas soil conditions and long term performance has not been established. |
| ♦ | Typically no soil test is performed on site. |
| ♦ | The piling depth is limited by the weight of the house, so piling may not reach stable soil. |
| ♦ | There is no steel reinforcement in the cylinders or cap. |
| ♦ | There is no test of piling cylinder concrete strength. Usually it is batch tested only. |
| ♦ | Cylinders broken during driving cannot be seen. |
| ♦ | Piling misalignment cannot be seen. |
| ♦ | There is no final inspection by city building inspectors. |
| ♦ | There is no design safety factor for each piling. |
| ♦ | Piling driving force may damage your house. (Your home's foundation, its weight and strength, is used as a fulcrum to drive piles into the soil.) |
| ♦ | Unconnected piling cylinders can not resist uplift. |
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Pressed Piling With Inserts Method
The pressed piling method had so many problems that the people who employed it were forced to come up with ways to fix some of its many drawbacks. The pressed piling with inserts method was one of the variations they came up with. The pressed piling with inserts method uses the same basic technique as the pressed piling method, with one minor change: the concrete cylinders are reinforced in one of several ways (usually with a piece of rebar) to stabilize them as they are driven into the soil.
While this somewhat helped with individual misaligned pilings, the new method did not only fail to fix any of the other drawbacks of the system, but it introduced two new ones as well: Instead of having a single cylinder misaligned, the entire piling could now be skewed, and moisture seeping into the gaps can cause the soil to weaken even further.
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Advantages
| ♦ | There is no waiting for the concrete to cure. |
| ♦ | The total job time is short. |
| ♦ | The cable or rebar inserted during driving helps alignment. It is of little benefit if inserted afterward. |
Disadvantages
| ♦ | There are no published capacity tests in Texas soil conditions. The long term foundation slab repair performance is not established. |
| ♦ | Typically there are no soil tests on site. |
| ♦ | The piling depth is limited by the weight of the house, so piling may not reach stable soil. |
| ♦ | There is no steel reinforcement in the cylinders or cap. |
| ♦ | There is no test of piling cylinder concrete strength. Usually it is batch tested only. |
| ♦ | There is no design safety factor for each piling. |
| ♦ | Cylinders broken during driving cannot be seen. |
| ♦ | There is no final inspection by city building inspectors. |
| ♦ | There is no design safety factor for each piling. |
| ♦ | Piling driving force may damage your house. (Your home's foundation, its weight and strength, is used as a fulcrum to drive piles into the soil.) |
| ♦ | Water flowing down the central hole weakens the soil. |
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Steel Piling Method
The steel piling method is similar to concrete pilings and attempts to use the strength of steel to overcome the weaknesses that arise with the concrete methods. Pressed steel pilings are primarily used in the Austin, Dallas, Fort Worth, and San Antonio areas where conditions are dryer and soils are sandy or in ground with harder soil strata between clay layers which would normally be the refusal point (the point where it takes more force to press the piling deeper than it does to lift the house) for concrete pilings.
Steel pilings over all are similar to the two other piling methods with two notable differences. First, they have the benefit of being able to be driven deeper into the ground before refusal, which can be a major advantage in dryer soils. Unfortunately, they are frequently not pushed all the way to the refusal point, which means they could sag and fail to properly support the home. The other major difference is that the thinner pilings have less ability to resist the forces of shifting soil, especially upheaval, which can cause severe damage to a home’s concrete slab.
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Advantages
| ♦ | There is no waiting for the concrete to cure. |
| ♦ | The total job time is short. |
Disadvantages
| ♦ | Reliability varies with the season of the year in which the work is done. |
| ♦ | Only perimeter installation is available. |
| ♦ | No soil tests are performed on site. |
| ♦ | The piling depth is limited by the weight of the house, so pilings may not reach stable soil. |
| ♦ | No onsite testing of piling strength is performed. |
| ♦ | Piling misalignment cannot be detected. |
| ♦ | Bending of installed segments upon installation cannot be seen. |
| ♦ | No predicted design safety factor for each piling. |
| ♦ | Not inspected by engineers or city officials. |
| ♦ | Piling driving force may damage the house. |
| ♦ | Unconnected piling segments cannot resist uplift. |
| ♦ | Method creates a long term loss of stability proven by experience and research. |
| ♦ | Rearranging heavy items inside the home may cause foundation movements. |
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