Earlier this year one of my neighbors (Roy) had foundation repair done on his concrete slab. The hot dry summer drought had done its damage and resulted in some of the classic signs of foundation movement.
You could see separation of the brick veneer away from the window frames in the front of the house and by the garage door. There was a big diagonal crack (half inch or so) in one of the sheet rock walls in a small office inside the garage area. Similar cracks had developed inside the house proper.
With the cost of foundation repair in mind, Roy called three foundation repair companies for bids.
The foundation companies all suggested piers for the front and both sides of the house.The company Roy picked uses pushed concrete piers, a very common foundation repair method in Texas.
To be sure, there are pros and cons with this method of underpinning. The structural engineer who inspected my foundation doesn’t like this method because you can’t thoroughly inspect the work like you can a drilled or bell bottom concrete pier.
When you push the concrete cylinders into the ground one on top of the other you can never be 100 per cent certain that one of them hasn’t broken or hit a rock and shot off course.
Some foundation repair companies will bind their stacks of cylinders together with steel cables as a safeguard against a failure of the concrete piers. And of course doing so adds to the cost of foundation repair.
The way this method of underpinning works is that piers are created by pushing these pre-cast concrete cylinders (or caissons) into the ground with a hydraulic jack using the edge of the slab foundation as a fulcrum. Hence the term “pushed piers.”
After a starter hole big enough for a crew member to get down into is dug, the cylinders are stacked on each other one by one and shoved into the ground until either bedrock is reached, or more commonly, the “point of refusal” is achieved. This simply means the pier won’t go any deeper and the hope is that it has reached a depth that is not affected by weather. After all, it is the shrinking and swelling of our heavy clay soils by wet weather and dry spells that cause a lot of foundation problems to begin with.
After the piers are set, the next step is to add blocks between the pier and the slab and have steel shims ready to go. The foundation is carefully raised with jacks and the shims are added between the slab and the piers to finish off the underpinning.
If everything goes right, the foundation is leveled and the cracks in and around the house are closed up. The sheet rock will still need to be touched up, but the closing of cracks are noticeable.
In Roy’s case, the job took two days. His cost of foundation repair was $5200. I think he said there were 13 piers installed which would come out to $400 per pier which falls in the average range for this kind of pier in our area. Two of the piers were installed inside the office which meant cutting through the slab, doing the piers, then repairing the hole.