Why Method Selection Comes Last, Not First
The order matters. Measure, then diagnose, then select a method. Reversing that sequence, picking a system and fitting the property to it, is the single most common failure in this industry.
This guide describes the main categories of foundation repair so you can follow a proposal and ask useful questions about it. What it deliberately does not do is tell you which method your house needs, because that determination comes from an on-site assessment of your specific property. Our slab foundation repair page covers how that assessment feeds into a scope.
The Four Categories
Almost all residential foundation work falls into one of four groups.
1. Underpinning with piers
The dominant approach for slab-on-grade foundations. The principle is straightforward: the foundation is currently supported by surface soil that has proven unreliable, so the load is transferred to something deeper and more stable.
Piers are installed beneath the grade beam, driven or formed down to a competent bearing stratum, and brackets transfer the structural load onto them. Once piers carry the load, seasonal movement in the surface clay no longer moves that part of the structure.
Within this category the systems differ by material and installation method, which is the subject of most of the discussion in a proposal.
2. Leveling and support adjustment
The dominant approach for pier-and-beam foundations. Rather than reaching deeper, the work restores or adjusts support beneath the existing structure: re-shimming beams over sound piers, rebuilding pier footings that have settled, and replacing framing members that have failed.
Leveling also describes the lifting phase of a slab underpinning project, which is part of why the terminology is confusing. The word describes an elevation outcome, not a single technique.
3. Drainage and moisture management
Not a structural repair, but genuinely a foundation method in the sense that it addresses the mechanism. Expansive clay moves because moisture changes unevenly. Drainage work, grading, and roof water management make moisture more consistent around the perimeter, reducing the driver of future movement.
It does not lift anything, and a company presenting it as an alternative to structural repair on a foundation that has already moved is overselling.
4. Crack and component repair
Epoxy injection, polyurethane sealing, carbon-fiber reinforcement, and masonry repointing address the material rather than the support. Appropriate where the underlying movement has stopped or where water exclusion is the objective. Applied to an actively moving structure, these repairs fail.
Pier Systems in More Detail
Since underpinning accounts for most slab work, the pier systems are worth distinguishing.
Steel push piers. Hollow steel sections driven hydraulically beneath the grade beam, using the structure’s own weight as reaction, advancing until gauge pressure records refusal on a bearing stratum. Depth is an outcome rather than a preset, which suits sites where depth to competent material varies. Covered in detail in our guide on steel pier systems.
Concrete pressed pilings. Precast cylindrical segments pressed in a stack beneath the beam. A long-established Texas approach, distributing load over a broader bearing face, well suited where competent material is reached at moderate depth.
Helical piers. Steel shafts with helical plates screwed into the ground with a torque motor, where installation torque correlates with capacity. Used where a driven system is impractical or where a lighter structure cannot provide adequate reaction.
Drilled and belled piers. Formed in place, typically under an engineer’s design, with a widened base to increase bearing area. Less common in residential retrofit than in new construction.
Our comparison of steel piers against concrete piers sets the two most common systems side by side on the same criteria.
What Actually Determines the Selection
| Factor | How it influences the method |
|---|---|
| Foundation type | Slab points to underpinning; raised points to support adjustment |
| Depth to bearing stratum | Deep or variable depth favours systems that follow refusal |
| Structural load | Heavier loads change capacity requirements per support point |
| Soil behaviour | Expansive clay, fill, and rock each change the calculation |
| Access | Narrow side yards, slopes, and utilities constrain equipment |
| Interior involvement | Whether interior load lines need support, and how to reach them |
| Engineering requirement | A sealed design may specify the system |
| Slab construction | Post-tensioned slabs constrain where work can occur |
The question worth asking
When a contractor proposes a system, ask why that one for this property. A good answer references your elevation profile, the expected depth to bearing material, and your access conditions. A weak answer describes the system’s general merits. The difference tells you a great deal.
What No Method Can Promise
No foundation repair guarantees that no future movement will occur anywhere on a structure. Soil continues to respond to moisture, weather, drainage, vegetation, and site changes. What a repair does is transfer load away from the unreliable material in the area addressed.
Be cautious of permanence language. A well-documented warranty with clear coverage, exclusions, and transfer terms is worth considerably more than a promise that sounds absolute and turns out to exclude everything outside the repaired zone.
Where to Go Next
If you want to understand how underpinning physically works on a slab, start with our slab repair material. If you are weighing two proposals that name different systems, the pier comparison guide is the more useful read. If you are earlier than that and simply trying to work out whether anything is wrong, measurement comes first and method comes later.