Foundation contractors sometimes offer up to three methods of underpinning a house foundation. These three main methods of repair include pushed concrete piers, steel piers and the drilled or bell bottom pier.
I’ve run across one company that says the bell bottom pier is the best way to go. It is the oldest method, most tested and most reliable form of underpinning a house with foundation problems. It is the type of pier used in highway and major commercial construction and has been for years. The company is Dawson Foundation Repair and has locations across Texas.
A Slab Foundation on Heavy Clay Soil is Subject to Movement
During the rainy season, clay soils expand with the added moisture. When the soils dry out the clay soils shrink. This can cause not only up and down movement of your foundation but also lateral movement. And this can cause the classic signs of foundation problems…diagonal cracks in the walls, inside and out, doors and windows that don’t work right and uneven floors. The Dawson folks say that if the foundation does need piers, the old fashioned bell bottom pier is the way to go.
Bell Bottom Piers Can Be Inspected for Integrity
That’s one advantage over pushed concrete piers or pushed steel piers. Pushed piers use the weight of the house or building as a fulcrum while pre-cast concrete cylinders or steel pipes are shoved into the ground by hydraulic jacks to the point of refusal…meaning they won’t go any deeper. The assumption is if the piers won’t go any deeper then they must have reached bedrock or a layer of stable soil. But how do you know that? And how do you know if one of the concrete cylinders broke on the way down or if a steel pier (basically a three inch pipe) didn’t bend and loose integrity? Just saying.
The Bell Bottom Pier on the other hand can be inspected throughout the installation process. After the soil is tested, a much bigger hole is dug to the depth required to reach stable strata under the edge of the slab foundation. That depth can be inspected and tested.
Building the Bell Bottom Pier
Then forms are built to contain the concrete for the pier, steel re-bar is placed in the forms for reinforcement and high strength concrete is poured into the form and allowed to cure. All of this can be inspected along the way.
After the piers have cured (7-10 days or thereabout ) the slab foundation can be carefully raised with jacks, then concrete blocks and steel shims fill the gap between the new piers and the concrete slab.
The Dawson website goes into much more technical detail about the construction of bell bottom piers. I’m happy to let them do the explaining because I’m just a writer and homeowner. And yes, the downside is that waiting period for the concrete to cure. But the claim is that you end up with a bigger wider stronger pier that can be inspected for proper construction during the whole process and resists lateral soil movement better the other common underpinning methods. I suppose if the bell bottom pier is good enough for highway overpasses it’s good enough for a house foundation.