Drilled Piers vs. Piles | Richardson Foundation Repair and Leveling

Concrete Pier Installations for Residential Structures:

A concrete pier is constructed by drilling a hole in the ground. Concrete is poured into the hole with reinforcing steel (rebar) added to give the pier strength in tension. The hole can be as big in diameter and as deep as necessary. A concrete pier can provide a sufficient safety factor to prevent future settling or heaving of the pier. A Safety Factor at the time of installation is usually designed to be from 1.2 (will support 120% of the weight of the structure) to 1.5 (will support 150% of the weight of the structure). Concrete piers drilled to a depth of 9 feet below the bottom of a perimeter beam in typical subdivisions are well below the soil's active zone and are not subject to seasonal moisture changes and soil movement.

Concrete Pressed Pile Installations for Residential Structures:

Concrete pressed piles are typically installed by using the weight of the house as the resistive force against which hydraulic jacks push (press) the piles into the ground. They are pushed to "refusal". This means that the pile will be forced into the ground until it begins to lift the house, at which time they can no longer be pushed farther into the ground. The Safety Factor at the time of installation is 1.0

The depth to which they are pushed is dependent upon the resistive force of the soil (skin friction and end bearing) at the time of installation, and the resistive weight of the house. If the depth to which the piles are pushed is insufficient to account for changes in the soil's capacity to support the weight of the house, THEY WILL “FAIL". Pressed piles are typically from 6" to 8" in diameter. The larger the diameter of the pile and the drier the soil, the shallower the resulting installation.

Steel Pile Installations for Residential Structures:

Steel pressed piles are typically installed by using the weight of the house as the resistive force against which hydraulic jacks push (press) the piles into the ground. They are pushed to "refusal". This means that the pile will be forced into the ground until it begins to lift the house, at which time they can no longer be pushed farther into the ground.

The depth to which they are pushed is dependent upon the resistive force of the soil (skin friction and end bearing) at the time of installation, and the resistive weight of the house. The drier the soil, the shallower the depth of the pile. If the depth to which the piles are pushed is insufficient to account for changes in the soil's capacity to support the weight of the house, i.e. within the soils active zone, THEY WILL “FAIL".

Steel pressed piles are typically from 2-7/8" to 3-1/2" in diameter. Some steel piles are open ended and some have solid ends or caps. The larger the diameter the pile, the shallower the resulting installation. Steel pressed piles are typically driven to depths below the soil's active zone since the skin friction and end bearing resistances are less than those of concrete pressed piles. The Safety Factor at the time of installation is 1.0 (they will hold only 100% of the weight of the structure).

Helical Pile Installations for Residential Structures:

Helical Piles were introduced in the Dallas/Fort Worth Metroplex in the 1990's, by A. B. Chance of Atlanta, Georgia. A helical anchor/pile is a segmented deep foundation system with helical bearing plates welded to a central steel shaft. Load is transferred from the shaft to the soil through these bearing plates. Central steel shafts are available in square shaft 1-1/4" to 2-1/4", or round shaft from 2-7/8" to 4-1/2". The helix sizes can range from 6" to 14" in diameter.

The helical pile is screwed into the ground using mechanical means with shear pins in a rotary mechanism to achieve the desired torque. The Safety Factor at the time of installation is indeterminate, as the depth to which they are screwed is dependent upon the resistive force of the soil at the time of installation. If the depth to which the piles are screwed is insufficient to account for changes in the soil's capacity to support the weight of the house, or if it terminates within the active zone, THEY WILL “FAIL" as they will move with the active soil.

Since the piles are screwed into the ground, they loosen the soil as they are screwed into the ground, thus their primary ultimate capacity is in end bearing.