Start With the Right Framing
These two options are not comparable alternatives in the way the question implies. They address different problems.
Repair addresses a support problem. The concrete is sound, the ground beneath part of it has moved, and piers transfer load to a stable stratum.
Replacement addresses a concrete problem. The slab itself has lost structural integrity and cannot be made to perform regardless of what supports it.
In residential work across San Antonio, the first situation is overwhelmingly common and the second is rare. If you are being told your slab needs replacing, the first question is what evidence indicates the concrete has failed rather than the ground beneath it. Our foundation evaluation page covers what an assessment establishes.
What Repair Involves
Piers installed beneath the grade beam, driven or pressed to competent bearing material, load transferred onto them, and a controlled lift bringing the structure back toward level. The existing slab stays in place throughout and continues to do its job.
Disruption is confined to excavation at pier locations, the lift itself, and any interior access required. The household usually stays in the house. Our slab foundation repair page covers the process in full, and our guide on how slab foundations are underpinned with piers explains the underpinning mechanism itself.
What Replacement Involves
A genuinely major undertaking:
- The structure is temporarily supported, since it will have no foundation.
- The existing slab is demolished and removed.
- Subgrade is prepared, which may include removing and replacing unsuitable material.
- Forms and reinforcement are placed.
- The new slab is poured and cured.
- The structure is set down onto the new foundation.
- Everything that sat on the slab is reinstated: flooring, fixtures, plumbing connections, and interior finishes affected by the process.
The household is out of the house. The timeline runs to weeks rather than days. The cost is a multiple of a repair, and engineering involvement is a given rather than a possibility.
When Replacement Is Genuinely Warranted
The criteria are about the concrete, not the movement.
- Structural failure of the concrete itself. Not cracking from movement, but concrete that has lost integrity through material failure.
- Extensive deterioration. Severe spalling, delamination, or degradation across a large proportion of the slab.
- Reinforcement corrosion at scale. Where corroding steel has caused widespread concrete damage rather than isolated spalling.
- Construction so deficient that repair is not viable. Rare, and usually identified through engineering assessment.
- A combination with other factors. A severely compromised slab in a structure undergoing major renovation, where the economics change.
Note what is not on the list: significant settlement, extensive cracking from movement, or a floor that is substantially out of level. Those are support problems and they are addressed by underpinning.
Side by Side
| Repair (underpinning) | Replacement | |
|---|---|---|
| Addresses | Support failure | Concrete failure |
| Existing slab | Retained | Demolished |
| Occupancy | Usually maintained | Not possible |
| Typical duration | Days | Weeks |
| Relative cost | Baseline | A substantial multiple |
| Engineering | Sometimes required | Effectively always |
| Permits | Often required | Required |
| Frequency in residential work | Common | Rare |
A caution worth stating
Replacement is sometimes raised in sales conversations as a way of making a repair proposal feel proportionate by comparison. If replacement is mentioned, ask directly what evidence indicates the concrete itself has failed, and ask whether an engineer has assessed it. An answer that describes cracking and unevenness is describing movement, and movement is a repair conversation.
Partial Replacement
Between the two extremes sits a middle option that is occasionally appropriate: removing and repouring a defined section of slab while retaining the rest.
This can apply where a specific area has deteriorated, often in a garage, a utility area, or a section that was added later and built to a lower standard. It is a much smaller undertaking than full replacement and it is sometimes combined with underpinning of the surrounding area.
Where it applies, the scope should be explicit about the boundary of the section being replaced, how it will tie into the retained slab, and what happens at that junction.
How the Determination Is Made
An evaluation assesses both the elevation profile and, where it is visible or can be exposed, the condition of the concrete. Those are separate findings.
A house with substantial differential settlement and structurally sound concrete is a repair. A house with modest movement and genuinely deteriorated concrete may be a different conversation. In practice the first is what we find, and the second is uncommon enough that we would want engineering input before recommending it.