Slab Foundation Repair in San Antonio, TX

What Is Slab Foundation Repair?

Slab foundation repair stabilises and, where practical, lifts a slab-on-grade foundation that has moved. Most San Antonio homes built from the 1960s onward sit on a slab-on-grade: a single concrete pour placed directly on prepared ground, thickened at the perimeter and along interior load lines into what is called a grade beam. The slab carries the walls, and the ground carries the slab. When the ground under one part of it changes, the slab follows.

It is the most common foundation type we encounter in foundation repair across San Antonio, and the one most often affected by the region’s expansive clay.

Repair works by taking that load off the soil and transferring it to something deeper and more stable. Piers are installed beneath the grade beam, driven down to a load-bearing stratum, and the structure is then supported on the piers rather than on the surface clay. That is the whole mechanism. Everything else is a question of which pier system, how many, where, and how deep.

Why slabs move here

San Antonio sits on a mix of expansive clay soils and, toward the Hill Country, shallower limestone. Expansive clay changes volume with moisture. It swells when wet and shrinks when it dries, and it does so unevenly across a lot because moisture is never uniform. One side of a house has a shaded flower bed and a downspout; the other has full afternoon sun and a mature oak drawing moisture out of the subgrade. Over years, that difference becomes differential settlement, and differential settlement is what cracks a wall.

Movement is not always downward. Where moisture accumulates under the interior of a slab, often because of an under-slab plumbing leak, the centre can rise. That is center heave. Where perimeter clay swells sharply after a wet season, the edges can lift. That is edge lift. Distinguishing among settlement, center heave, and edge lift changes the repair plan completely, and it is not something anyone can establish from a photograph of a crack.

What Does the Evaluation Examine?

Before any repair is proposed, we take slab elevation measurements across the entire floor plan. Readings are recorded room by room and plotted so the relative differences are visible as a profile rather than a list of numbers. That profile is what tells us whether the low point is a corner, an edge, or the perimeter as a whole, and therefore what shape the movement has.

Alongside the measurements we look at:

• Interior observations: crack locations and patterns, door and window operation, separation at trim and baseboards, floor slope.
• Exterior observations: brick and mortar cracking, separation at window and door frames, visible slab edge condition.
• Site conditions: grading and fall away from the foundation, downspout discharge, irrigation placement, standing water, and soil bearing capacity where it can be observed.
• Tree proximity and evidence of root-related soil moisture loss near the perimeter.
• Any indication of plumbing involvement, which may prompt a recommendation for a hydrostatic plumbing test.
• Records of previous foundation work, including existing piers and any transferable warranty.

The output is a findings summary and, where repair is warranted, a proposed scope. If the readings do not support repair, that is the finding, and we will say so.

Types of Slab Repair Systems

Steel push piers

Steel push piers are hollow steel sections driven hydraulically, one section at a time, beneath the grade beam using the weight of the structure as resistance. They advance until the gauge records a refusal pressure indicating the pier has reached a competent load-bearing stratum. Because depth follows the ground rather than a preset number, steel push piers suit sites where a suitable stratum is deep or where depth varies across the foundation. Pier installation depth is recorded during installation and forms part of the project record.

Concrete pressed pilings

Concrete pressed pilings are precast cylindrical segments pressed into the ground in a stack beneath the grade beam. They are a long-established approach in Texas, distribute load over a broader bearing face, and can be appropriate where a competent stratum is reached at moderate depth. They are less suited to sites requiring substantial depth, because each added segment increases the risk of misalignment in the stack.

Drilled and belled piers

Where an engineered solution calls for it, drilled piers formed in place can be specified, typically under an engineer’s design. These are less common in residential retrofit work than push piers or pressed pilings but appear in some scopes, particularly where an engineer has designed the repair.

Neither steel nor concrete is universally superior. Our guide comparing steel piers and concrete piers sets them side by side on the same criteria, and the selection for your property comes out of the evaluation.

Perimeter and Interior Pier Placement

Most slab repairs begin at the perimeter, because the grade beam runs there and access is from outside. Perimeter piers are installed in excavated pits, brackets are attached to the grade beam, and load is transferred to the pier.

Interior pier placement is a different proposition. Reaching an interior load line means either opening the floor from inside or tunnelling beneath the slab from outside. Interior access is often faster but removes flooring in the work area. Under-slab tunnelling protects interior finishes but adds excavation time and cost. Which is chosen depends on the elevation profile, the flooring in question, and what else is happening on the project. Our guide comparing under-slab tunnelling with interior access sets out the trade-offs.

On post-tensioned concrete slabs, interior work requires locating tendons first. Cutting a tensioned tendon is dangerous and expensive. This is one of the practical reasons the slab type is established early rather than assumed.

Hydraulic Lifting and Progressive Recovery

Once piers are in place, hydraulic lifting raises the structure in controlled increments. Jacks along the pier line are operated together so load transfers gradually and the slab moves as a unit rather than at isolated points.

The realistic objective is progressive recovery: bringing the structure back toward level within practical limits, with the foundation then supported on piers rather than on surface clay. It is not a return to new-construction flat, and any proposal promising that deserves a second look. Some sheetrock relief cracking and trim movement is normal during a lift. The written scope states which cosmetic repairs, if any, are included.

What Affects Scope and Cost

The factors that move the number are consistent and worth understanding before you compare proposals:

Factor	Why it changes the cost
Pier count	Each pier carries material, labour, excavation, and backfill
Pier installation depth	Depth follows refusal, not an estimate; deeper means more material and time
Interior versus exterior access	Interior piers mean flooring removal or tunnelling
Excavation conditions	Rock, wet clay, utilities, and tight access all slow excavation
Engineering	An engineer’s design or letter, where required, is a separate cost
Permits	Requirements depend on scope and jurisdiction
Associated work	Hydrostatic plumbing testing, drainage correction, or plumbing repair
Restoration	Backfill and rough grading is the baseline; anything beyond it is scope

A quote without these details is not comparable to one that has them. Our cost guide covers each factor with dated ranges and explains how to read a proposal, and our quote-comparison guide gives you a framework for setting two proposals side by side fairly.

When Slab Repair Is Not the Answer

Three situations come up regularly where repair is not what we recommend.

The first is cosmetic cracking with a flat elevation profile. If the readings show no meaningful differential, a crack is a crack. Document it, date the photographs, and re-check after a wet season.

The second is suspected plumbing-driven heave. If the profile suggests the centre is rising, lifting is the wrong first move. A hydrostatic plumbing test comes first, and the plumbing is addressed before any foundation work is considered.

The third is a structural question outside a contractor’s scope. Where a consequential structural conclusion is needed, or where a permit requires it, a Texas licensed professional engineer provides an assessment. That is a different document from our proposal, and we will say so rather than blur the line.

After the Work Is Done

Post-repair elevation documentation records the floor profile once the lift is complete. Together with the written scope, the warranty terms, and any engineering correspondence, it forms the record of what was done. Keep it. If you sell the home, a buyer asking about the foundation will be reassured far more by a documented scope and a transferable warranty than by a verbal account of work that happened years ago. Our documented slab repair walkthrough follows one project from the first call through to that closing record.