The idea is simple. Soil near the surface moves more frequently than soil deeper in the ground, therefore if you can support the building on the soil that moves less frequently you will have less problems over the life of the structure. Once the house is supported on that stronger soil, we have the option to then manipulate the level of the foundation to lift it back to it’s original variance.
The tool we use to help support the structure is called the pier. There are many different types of piers in our industry. The most common and arguably best is the pressed piling family of piers. Within pressed pilings you have the options of two different types of materials, steel or concrete.
Find the right pier for your project.
PermaTech is here to make sure that you understand exactly what is needed for your foundation repair project, because each type of pier has its own strengths and weaknesses. Determining the right pier on the project is based on variables discovered during the initial inspection, where we take into account the soil type, weight of the house, customer price range and a few other factors. We promise never to recommend a type of pier that is not the right fit for you and your house. Below you will find additional information specific to the type of piers we install as well as what to consider when looking at other types of piers.
The concrete pressed piling is the most cost effective foundation repair solution on the market. It’s a series of pre-molded concrete pilings, measuring 6 inches in diameter and 12 inch tall. High strength concrete is used for the pilings that can take up to 12,000 PSI, well above what most homes will apply to it. The pilings are stacked on top of each other as they are pushed with a piece of steel rebar placed down the center to connect the pilings together. This rebar keeps single pilings from shifting or become misaligned during the process.
The concrete pressed piling is a friction based support system meaning that it gets it support from the force of friction down the sides of the pier. When we first start pushing, with our hydraulic ram, the piling and there isn’t much surface area in the ground the force of friction is well below the force from the weight of the house, therefore the piling is forced into the ground. As we start to get deeper and deeper the earth begins squeezing the sides of the pier and eventually the force of that friction is now more than the force from the weight of the house. We call this depth the point of refusal or the load bearing strata. Now instead of the pier being pushed into the ground the house begins to lift.
Since we push one pier at a time, but lift across many different piers at once we have a bit of wiggle room in case settlement occurs in the soil.
The concentrically loaded steel pier is considered the best pier you can install under a house for support. Just like the concrete pressed piling, the steel piers are sections of double walled steel pipe. They measure 2 and 7/8 inches in diameter and once stacked measure 12 inches tall. Instead of a piece of steel rebar down the center, the double pipe allows us to stagger the pipe so that each one fits snuggly within each other piece. This assures that the pier doesn’t become misaligned during the install process.
The steel pier installs much like the concrete pressed piling, except that since it’s much smaller and therefore has less surface area it’s able to push deeper and has a higher chance of hitting bedrock before the friction can stop the pier. This offers much more reliable support over the long run.
Through your research you might come across other less common types of piers or lifting mechanisms. Just as with ours, they each have their own set of strengths and weaknesses.
Drilled Pier or Concrete Pier
The drilled pier or concrete pier is installed by digging out a deep hole with an auger and filling it with concrete. When the concrete dries it becomes a pier. The downside to this is that most companies are limited by how deep they can dig by the auger they have. This often means that the pier is installed at a higher elevation than the point of refusal. This type of pier should really only be used for new buildings or for very light weight structures.
Bracketed Steel Piers
The bracketed steel pier is a type of steel pier that is installed from the side of the foundation and connected via a bracket or type of shelf. This type of pier can be installed with less manpower and a smaller amount of digging. Based on the offset force from the bracket, this can put undue stress on the pier and cause it to bend. Also the steel sticks out of the ground where it is more susceptible to corrosion.
This involves pumping a mixture of sand and concrete under the slab to lift it. While it’s effective at lifting very thin slabs, it doesn’t add any additional support and often added a significant amount of weight to the soil which will cause it to fail even faster next time.