Concrete piers are primarily made by digging holes down to the frost line, lining them with specialized fiber-form tubes, and then filling these lined holes with poured concrete. This method creates strong, durable foundations that can extend above ground for structural support.
The Essential Steps in Concrete Pier Construction
The creation of a concrete pier foundation is a straightforward yet crucial process for many structures, providing robust support by reaching stable ground below the frost line.
1. Excavating to the Frost Line
The initial and most critical step in making concrete piers involves digging holes down to the frost line. This depth is essential because it ensures that the bottom of the pier is below the maximum depth to which ground frost penetrates. When water in the soil freezes, it expands, causing the ground to heave. By extending below the frost line, the pier remains stable and unaffected by this frost heave, preventing structural damage to anything built upon it.
- Key Detail: The exact depth of the frost line varies significantly by geographical location and local building codes.
- Purpose: To prevent frost heave, which can lift and damage the foundation over time.
2. Lining with Round Fiber-Form Tubes
Once the holes are dug to the appropriate depth, they are first lined with round fiber-form tubes prior to pouring the concrete. These cylindrical tubes, often made from durable, wax-coated cardboard or similar materials, serve several important functions:
- Simplifying the Process: They create a smooth, consistent mold for the concrete, making the pouring process cleaner and more efficient.
- Shaping the Pier: The tubes ensure a perfectly round and uniform pier, which is beneficial for structural integrity.
- Preventing Soil Contamination: They prevent the wet concrete from mixing directly with the surrounding soil, which could weaken the pier.
- Facilitating Extension: As the reference states, using these tubes allows the piers to be cut to extend a specific height above the ground after the concrete cures.
3. Pouring the Concrete
After the fiber-form tubes are securely placed in the excavated holes, they are then filled with poured concrete. The concrete should be poured carefully to eliminate air pockets and ensure a solid, dense pier. Depending on the size and depth of the pier, rebar (reinforcing steel bars) may be inserted into the wet concrete to enhance its tensile strength and overall stability, though this is not explicitly mentioned in the provided reference.
4. Finishing and Above-Ground Extension
Once the concrete is poured and has begun to cure, the piers can be cut to extend above ground 6 to 12 inches. This elevated portion serves as a connection point for the structure's framing, keeping wooden elements away from ground moisture and potential pest issues. The fiber-form tubes, which protected the concrete during curing, can either be removed or left in place, depending on the type of tube and local practices.
Summary of Concrete Pier Components & Actions
| Component/Action | Description | Benefit/Purpose |
|---|---|---|
| Excavated Holes | Dug to the local frost line. | Ensures stability by preventing frost heave from lifting the foundation. |
| Fiber-Form Tubes | Round tubes used to line the excavated holes. | Simplifies the concrete pouring process, shapes the pier, allows for extension. |
| Poured Concrete | Concrete mixture filled into the lined holes. | Forms the strong, load-bearing pier foundation. |
| Above-Ground Cut | Piers are cut to extend 6 to 12 inches above the ground. | Elevates the structure, protecting it from moisture and pests. |
By following these steps, a durable and stable concrete pier foundation is established, providing reliable support for various construction projects.
