How do pressed concrete piles work and what are their limits?

Reviewed by Preston, Oklahoma foundation repair consultant · Updated 2026-10-14

In short: Pressed concrete piles are stacks of short precast concrete cylinders pushed into the ground under a foundation with a hydraulic jack, using the building's weight as the reaction, until they will not go further ¹. They are a long-used underpinning method, but stopping point ("refusal") is not the same as proving the pile reached stable soil, and the piles generally do not resist uplift from swelling clay ¹².

How does the system work?

A pile (or pier) is a column that carries a building's load down to firmer soil. Underpinning means adding piles under an existing foundation. With pressed concrete piles ¹:

• Segments are typically cylinders about one foot long. Diameters vary; guidance gives tapering 4-, 6- and 8-inch segments as an example.
• One segment at a time is pushed down by a hydraulic jack that pushes against the foundation above.
• Each pile is driven to refusal — the point where the force needed to drive it exceeds the load it will support.
• At refusal, the pile is shimmed under pressure before the jack is removed, to limit rebound. Shims are at least 1/8 inch thick.
• A precast cap of the same strength as the segments sits on top.
• Steel cable, rebar or rods may run through a center hole as optional reinforcement.

If piles are driven at the same time they should be at least 25 feet apart; otherwise one pile is driven at a time ¹.

What are the installation steps?

1. Dig an access hole at the foundation beam.
2. Press the first segment and keep adding segments under the jack.
3. Continue to refusal and record the depth and driving force or pressure ¹.
4. Set the cap and shims, then raise the foundation toward its target.
5. Backfill and compact the hole.

Guidelines call for driving records for each pile (depths, plus driving force or pressure if recorded), elevation surveys before and after, and a plumbing leak test report on under-slab lines ¹.

What spacing does published guidance show?

For lightly loaded homes, one engineering guideline gives prescriptive maximum spacing ¹:

Homes of three or more stories need an engineered design ¹. Spacing is covered in loads, pier spacing and capacity.

What are the limitations?

Refusal is not verified capacity

Refusal only shows the jack could not push further at that moment. Guidelines note that piles that do not reach stable soil below the active zone — the depth where soil moisture changes with the seasons — may not resist shrink or swell movement ¹. A committee review lists shallow piles losing skin friction (grip along the sides) during drought as a potential problem ². Oklahoma research using Mesonet data estimated active zone depths around the state at about 0.5 to 4 meters (roughly 1.5 to 13 feet) ³. A pile that stops in stiff, dry clay or soft weathered shale near the surface may still be inside that zone; see shale weathering and bearing strata.

When refusal comes before the minimum depth in the plans, the guideline's options include stopping with engineer approval, using a smaller pile at least three diameters away, water jetting, or pre-drilling a new hole ¹. A review notes that water jetting adds moisture that can cause heave ².

No uplift resistance

Pressed piles generally do not resist uplift, so where soil touches the foundation they will not stop swelling clay from lifting it ¹. Soils with a linear extensibility (an NRCS measure of shrink-swell) of 6% or more are rated high or very high shrink-swell ⁴. This is why these piles are not used to fix perimeter wetting heave.

Segment alignment

Without center reinforcement, segments can shift sideways; a committee review lists unreinforced segments moving laterally as a possible problem ².

Fill and debris

Guidelines call for removing obstructions encountered during installation, and note that dense granular soils and stiff sandy clay or clayey sand layers can make piles hard to drive ¹. Fill can hold such obstructions above native soil. See fill consolidation settlement.

How do they compare with steel push piers?

Steel push piers are installed the same way but use steel pipe, which can often be driven deeper. Oklahoma installation records for steel push piers at one large Tulsa site logged a median depth of about 12 feet, with the middle half between 9 and 14 feet ⁵. Details are on the steel push piers page.

Cost for any pier method is driven mainly by the number of piles, depth and access.

Related

• Steel Push Piers
• Method Selection Matrix
• Pier Uplift or Movement After Repair
• Lifting Procedure and Restoration
• Shrink-Swell and Active Zone