The steel pier is considered one of the top of the line types of piers to install under a foundation. As it's typically able to get the deepest penetration into our tough clays than any other. With more depth comes more stability and more longevity. We consider this system a permanent solution as it's lifespan is possibly going to be longer than the lifespan of the house. With that longevity comes a significant cost, as steel carries a much higher material cost and you ultimately need more of it if it's able to get deeper.
Our steel pier is considered a concentrically load, double walled, sleeve lock design. Concentrically loaded means that the pier stands straight up and down directly below the weight bearing beams of the foundation, this is opposed to other steel piers that are offset with a bracket. Double walled means that there's an interior and exterior pipe, giving you twice the strength and allow the pieces to interlock with each other. Sleeve lock design means that the exterior pipe and interior pipe are pre-clamped at the most effective spots to prevent the interlocked pieces to become loose as it's installed. For a steel pier we are also able to fabricate a bottom piece that acts as a friction reduction collar, carving out a slight bigger hole than the diameter of the pipe. This prevents friction build up. After installing the pipe the top of the pier works most the same way as a concrete pressed piling, only the top cap is also made of steel, then the shims are the same.
How are they installed?
First a hole must be excavated near a beam of the foundation. For most projects these holes are dug around the perimeter of the foundation from outside of the house, however sometimes they need to be installed inside the house. This hole is approximately 30 inches wide by 30 inches long and the depth is about 24 inches below the bottom of the foundation, which could end up making the hole 48 to 54 inches deep. We also need to excavate 6 to 10 inches under the house to allow us access directly below the bottom of the slab. We then can start pushing pipe.
You use a hydraulic press to push these pipes into the ground one by one, interlocking each piece to help keep it aligned. These pipes are pushed until we reach the point of refusal. For a steel pier this is the depth in the ground that typically the bottom of the pier can sit on something solid, bedrock or limestone depending on the area. This is opposed to a concrete pier than typically floats in the clay as it's point of refusal is much closer to the surface
Once this point of refusal is met for all the piers we are installing, we place the top cap on top of the last cylinder and place a 20 to 30 ton bottle jack to the right or left side of the top of the cap. The heavy duty bottle jack can then lift the house back into place. We then replace the bottle jacks with various assorted concrete blocks to shim up to the bottom of the slab with the last shim being a steel shim to help secure the pier to the house.
Most people choose the steel pier in situations where they plan on owning the home forever and never want to deal with foundation issues again. Since it is able to reduce that friction build up and sit the pier on something more solid than clay it will last a lifetime. This typically means depths averaging 25 feet in this metroplex. It also does not push on the bottom of the foundation as much as a concrete cylinder does since it doesn't build up friction, this means less potential for additional cracks as a result of installing piers.
The main drawback of installing this pier is typically the cost. It's usually the most expensive type of pressed piling and depending on the depth can even be more expensive than other methods. It's hard to estimate exactly what depth it will push so sometimes you might not even know what the final cost will be until we are finished. You are essentially purchasing peace of mind at a very high cost.