Slab Foundation Repair: Methods, Costs, and What to Expect

What Is a Slab Foundation?

A slab foundation is a single continuous concrete pour - typically 4-6 inches thick - that sits directly on the prepared subgrade. Most homes built in the South, Southwest, and parts of the Midwest use slab construction. Post-tension slabs (which have steel cables embedded under tension) are common in Texas and California.

Slabs are generally durable but are directly exposed to ground movement. Any significant change in the moisture content of the soil beneath - from drought, flood, plumbing leaks, or vegetation - can cause the slab to shift, crack, or heave.

If you are still deciding which foundation you have or want to understand how construction and repair differ between the two main residential types, see slab vs pier and beam foundations.

Post-Tension vs. Conventionally Reinforced Slabs

Two slab types dominate residential construction, and the difference changes how a repair is planned, priced, and sequenced.

Conventionally reinforced slabs use a grid of steel rebar, sometimes with welded wire mesh, cast into the concrete. The steel is passive: it carries tension only once the concrete tries to crack. These slabs can be cored in most locations with a standard masonry bit, which is why interior pier placement and under-slab plumbing access are comparatively simple.

Post-tension slabs contain high-strength steel cables, called tendons, running through plastic sheathing inside the concrete. After the slab cures, each tendon is stretched with a hydraulic ram and locked off at an anchor in the slab edge, holding the concrete in permanent compression. That compression lets a thinner slab bridge soft spots without cracking, which is why post-tension construction became the default across much of Texas, Arizona, Nevada, and California. Because tendons change how the slab can be cut and repaired, post-tension slab repair is covered in its own guide.

Why it matters for repair: a live tendon carries tens of thousands of pounds of stored force. Cutting one releases that force instantly, can eject concrete fragments, and leaves the surrounding strip of slab weaker than the engineer designed it to be. Every interior core hole, plumbing tunnel, and pier location on a post-tension slab has to be placed between tendons, which means the cables get mapped before any bit touches the concrete.

Two quick checks tell you which type you have. Look along the exposed slab edge or in the garage for small patched circles or rectangles roughly two inches across, which are the tendon anchor pockets. Many builders also cast a warning plaque into the garage slab telling future owners not to cut or drill. If neither is present and the home predates the mid-1980s, conventional reinforcement is the safer assumption until a scan confirms it.

Why Slab Foundations Fail

Understanding the cause of failure is essential because different causes require different repair approaches.

Soil Settlement

When the soil beneath a slab loses moisture (drought, root uptake, poor drainage), it shrinks and compresses. The slab loses support and can crack and sink in affected areas. This is the most common cause of slab foundation problems in Texas, Oklahoma, and the Southwest.

Expansive Soil Heaving

Expansive clays - particularly Blackland Prairie clay in Texas and Bentonite clay in Colorado - absorb water and swell. If moisture reaches the soil beneath the slab unevenly (from a plumbing leak, inadequate drainage, or irrigation), the slab can heave upward in isolated areas. Heaving and settling require different repair approaches.

Plumbing Leaks Under the Slab

Post-tension slab homes have plumbing embedded in or under the concrete. A slow slab plumbing leak can saturate and erode the underlying soil, creating voids beneath the slab that eventually cause it to crack and drop. Plumbing leaks must be repaired before foundation repair can be effective.

Poor Initial Compaction

Slabs built on inadequately compacted fill can settle as the fill material compresses under load over time. This is common in newer developments where cut-and-fill grading was done without adequate compaction testing.

Drainage Problems

Water pooling against the foundation or inadequate positive grade (slope away from the foundation) allows sustained soil saturation, which accelerates both expansion and erosion at the slab perimeter.

Edge Lift vs. Center Lift

Engineers describe slab movement by its shape, not only its direction, because the shape points directly at the cause.

Edge lift, also called dishing, means the perimeter of the slab sits higher than the middle. Moisture is concentrating around the outside of the house: irrigation beds against the wall, downspouts discharging at the foundation, a planter that never dries out, or a wet season following a drought. The interior floor reads as a shallow bowl, and drywall cracks tend to open toward the center of the house.

Center lift, also called doming, means the middle of the slab sits higher than the edges. Either the interior soil has swelled, with an under-slab supply or sewer leak being the classic cause, or the perimeter soil has dried and shrunk away, which happens when mature trees pull moisture from edge soil through a dry summer. Doors along exterior walls bind at the top corner, and cracks tend to run diagonally from interior corners out toward the perimeter.

A slab can also settle without lifting anywhere, and that uniform downward pattern is what piers are designed to correct. Telling settlement apart from heave is the most consequential call in the whole diagnosis: piers stabilize a slab that is dropping and do nothing useful for a slab being pushed upward. Foundation heave follows a different repair path built around removing the moisture source rather than adding structural support.

Signs Your Slab Foundation Needs Repair

Slab problems rarely announce themselves with one dramatic failure. They surface as a cluster of small annoyances appearing over a season or two, usually concentrated on one side of the house.

Inside the home

• Diagonal cracks running from the corners of door and window frames toward the ceiling
• Floor tile cracking along a line, or grout that keeps failing in the same joint after repair
• Interior doors that swing open or shut on their own, or that stick only in certain months
• Gaps opening where a wall meets the ceiling, or where the baseboard meets the floor
• Floors that feel sloped underfoot, confirmed when a marble rolls the same direction every time

Outside the home

• Stair-step cracks in brick veneer or block, particularly near corners and above openings
• Separation at the mortar joint where the brick ledge meets the slab edge
• A widening gap between the garage door frame and the slab, letting daylight through at one corner
• A driveway, walkway, or patio that has dropped away from the house, leaving a lip
• A horizontal crack in the exposed slab edge, or a section of edge that has rotated outward

Utility and moisture clues

• A water bill that climbs with no change in household use, which can point to an under-slab leak
• Warm patches on the floor, which suggest a hot water supply line leaking beneath the concrete
• A persistent damp or musty smell confined to one room of a slab home

Crack width gives you a rough triage rule. Hairline cracks under 1/16 inch are usually concrete shrinkage from the original cure and are not structural. Cracks between 1/8 and 1/4 inch are worth monitoring: draw a dated pencil line across the crack and check monthly for growth. Anything wider than 1/4 inch, or any crack where one side sits higher than the other, indicates active differential movement and deserves a professional look.

One symptom alone usually means very little. Lumber shrinks, houses settle in their first years, and a single drywall crack over a doorway proves nothing. Two or three of these signs appearing together, worsening across months, and clustered in one part of the house is the pattern that justifies an inspection. Stair-step cracks in masonry and sticking doors and windows are the two complaints that most often turn out to be genuine slab movement.

Slab Foundation Repair Methods

Drilled Pier Underpinning (Most Common)

Drilled piers - either helical piers or push/resistance piers - are installed through the slab edge or through holes cut in the slab. The piers are driven or screwed down to stable bearing capacity, then a bracket is used to lift and stabilize the slab.

Helical piers are screwed into the ground and can be installed in tight spaces. They’re suitable for lighter loads and are often used for interior settling.

Push piers are driven hydraulically into the ground using the weight of the structure. They’re typically used on the perimeter and require a minimum load to drive properly.

Cost: $1,000-$3,500 per pier installed. Most residential projects require 6-12 piers for a full repair; $6,000-$25,000 is a typical range for complete slab stabilization.

Mudjacking (Concrete Leveling)

Mudjacking injects a cement slurry or polyurethane foam beneath the slab to fill voids and lift sunken sections. It’s less expensive than pier installation and suitable for slabs that have minor settling but haven’t lost bearing capacity.

Limitations: Mudjacking does not address the underlying soil instability. On expansive clay soils, results may be temporary. It works better in stable-soil areas where the slab has sunk due to void formation rather than ongoing soil movement.

Cost: $500-$3,500 depending on area and number of injection points.

Polyurethane Foam Injection

A modern alternative to mudjacking, foam injection fills voids more precisely, weighs less (reducing further settling risk), and cures faster. Used for smaller slab areas and interior floors.

Cost: $500-$2,500 depending on extent.

Drainage Correction

For heaving slabs caused by uneven soil moisture, drainage improvement is the primary treatment. This includes regrading, French drain installation, gutter extension, and irrigation management. Structural repair is ineffective if the moisture problem isn’t resolved first.

Slab Repair Methods Compared

No single method fixes every slab. The table below maps each option to the conditions it actually solves, which is the fastest way to sanity check a contractor’s recommendation against what your house is doing.

Methods are frequently combined. A common real-world scope is perimeter push piers on the settling side, a handful of interior helical piers under a load-bearing wall, and gutter plus grading work to keep the soil moisture steady afterward. If a contractor recommends piers, understanding helical piers vs push piers helps you judge whether their choice fits your soil and access conditions.

How a Contractor Decides Which Method You Need

A credible recommendation rests on measurements, not on a walk-through and a quote written on the hood of a truck. Four diagnostic steps should precede any proposal.

Elevation Survey

The contractor or engineer runs a floor elevation survey with a manometer or laser level, taking readings on a grid across the finished floor and recording each point relative to a benchmark. The output is a contour map of the slab showing where the high and low points sit and how much total deflection exists.

This map answers the two questions everything else depends on: how much the slab has moved, and in what shape. A dish pattern points at perimeter moisture, a dome points at interior swelling or a leak, and a single low corner points at localized settlement. Residential slabs are rarely dead flat even when new, so the survey is read for pattern and slope rate rather than absolute numbers. Deflection in the range of 1 inch across 20 feet in a consistent tilt is generally where contractors start treating movement as significant.

Plumbing Leak Testing

Before anyone quotes piers, the under-slab plumbing should be cleared. A static test plugs the drain system and fills it to slab level to see whether the water holds, and a pressure test isolates the supply lines to check for loss. Some contractors add a camera inspection of the sewer line to locate breaks and separations.

Skipping this step is the most expensive mistake in slab repair. Piers installed over soil that is still being saturated by a leaking line will hold their position while the surrounding soil keeps swelling or washing out, and the homeowner pays twice.

Soil Conditions

Soil determines how deep the piers must go and how the slab will behave after the work. Contractors look at the local plasticity index (a measure of how much a clay expands and contracts with moisture), the depth to competent bearing material, and the history of fill on the lot. In heavy clay regions, competent bearing may sit 12-25 feet down, while in areas over sand or weathered rock it can be much shallower. On larger or contested jobs, a geotechnical boring gives real numbers instead of regional assumptions.

Site and Moisture History

Good diagnosticians ask about the story of the house: when the cracks first appeared, whether they open and close with the seasons, when trees were planted or removed, whether irrigation runs against the foundation, and whether the neighborhood was built on cut-and-fill. Seasonal movement suggests a moisture management problem, while movement that only progresses in one direction suggests genuine settlement.

If the picture is ambiguous or the repair is likely to be large, an independent structural engineer’s report is money well spent. A foundation inspection from someone who does not sell repairs gives you a scope of work you can bid out to multiple contractors on identical terms.

What to Expect During Slab Repair

1. Assessment: Contractor assesses the slab with a laser level to map differential movement. They may check for plumbing leaks with a pressure test before structural work.
2. Access: For perimeter pier installation, small access holes are dug at the slab edge. Interior piers require 12-18 inch core holes drilled through the slab.
3. Pier installation: Piers are driven or screwed to refusal depth. A bracket is attached to the footing.
4. Lifting: Hydraulic jacks lift the structure to target grade. Not all slabs can be lifted to original grade - aggressive lifting can crack plumbing connections.
5. Grouting and patching: Core holes are filled with concrete. Access pits are backfilled and compacted.
6. Cleanup: Most contractors leave the work area broom-clean. Landscaping disturbed during access may need restoration.

Interior vs. Exterior Pier Placement and What Gets Disturbed

Where the piers go determines how invasive the job feels from inside the house.

Exterior perimeter piers are installed from outside. The crew hand-digs or machine-digs access pits along the foundation, roughly 3 feet by 3 feet and 2-4 feet deep, spaced according to the engineered pier layout. What gets disturbed is the yard: shrubs and flower beds within a few feet of the wall usually have to come out, sod is lifted, sprinkler lines in the trench path are commonly cut and spliced back, and fences may need a section removed for equipment access. Expect the working strip along that wall to look rough for weeks even after backfill, because the soil settles as it re-compacts. Contractors generally backfill and rough-grade but do not replant, so budget separately for landscaping restoration.

Interior piers are installed from inside the living space. The crew removes flooring in the work area, cuts a core hole through the slab (usually 12-18 inches across), excavates by hand beneath it, then drives or screws the pier and sets the bracket. What gets disturbed is your finished floor. Tile, hardwood, and laminate over the core locations will not survive the cut, and the surrounding material is often damaged during removal. Carpet can usually be pulled back and re-stretched. Furniture must be cleared from the room, drywall dust travels, and the noise of a core drill and jackhammer inside the house is significant.

Interior work also runs slower and costs more per pier than perimeter work, because the crew has to protect the home, extract spoil by bucket, and work in confined space. Contractors reach for interior piers when the elevation survey shows the low point under a load-bearing wall or in the middle of the house, where perimeter piers cannot pick up the load. Ask any contractor proposing interior piers to explain, using the elevation map, why the perimeter alone will not do the job.

Tunneling as an Alternative

On some jobs, especially where a homeowner refuses to give up finished floors or where under-slab plumbing needs repair anyway, crews dig access tunnels from outside the house inward beneath the slab. Tunnels keep all the mess in the yard and leave the interior untouched. They cost more, take longer, and require careful backfill and compaction so the tunnel itself does not become a future void, but for a home with expensive interior finishes the trade is often worth it.

How Long It Takes and Whether You Can Stay Home

Most residential slab repairs run 2-5 days on site. Perimeter-only pier jobs of 8-12 piers frequently finish in 2-3 days. Add interior piers, tunneling, or plumbing repair and the window stretches to a week or more. Weather matters: heavy rain floods access pits and halts excavation.

You can usually remain in the home throughout. Water and power stay on, and crews work standard daytime hours. The realistic disruptions are noise from hydraulic equipment and core drilling, dust inside if interior work is happening, restricted access to the rooms being worked in, and blocked driveway or yard access while equipment and spoil piles occupy the site. Households with someone working from home, an infant napping, or a noise-sensitive pet often plan to be elsewhere on the loudest days.

If plumbing under the slab has to be replaced, you may lose water service for part of a day or more. Confirm the schedule in advance. Contractors handling a full foundation leveling scope on a larger house should give you a written day-by-day plan before work begins.

Cosmetic Repairs After the Structural Work

Foundation repair stabilizes the structure. It does not restore the finishes, and almost no pier contract includes cosmetic repair unless you negotiate it in writing.

When a slab is lifted, the walls, doors, and trim move with it, which reopens some cracks, closes others, and can create new ones. That is normal. The standard advice is to wait 30-60 days after the lift before doing cosmetic work, so the structure and soil can settle into their new position and any remaining movement shows itself.

Typical follow-up work includes patching and repainting drywall cracks, re-caulking where trim separated, resetting or replacing cracked tile, planing and rehanging doors that no longer sit square in their frames, tuckpointing stair-step cracks in exterior brick, and replacing the flooring cut out over interior pier locations. On a mid-size job this commonly adds $1,500-$6,000, and more if custom tile or hardwood has to be matched. Ask each bidder plainly whether cosmetic repair is included, excluded, or offered as an add-on, because that single line item explains a large share of the spread between quotes.

Repairing a Post-Tension Slab

Post-tension slabs are repairable using the same pier methods, but the sequence includes steps a conventional slab does not need.

Locating the tendons comes first. Crews scan the slab with ground-penetrating radar or an electromagnetic locator and mark the cable runs on the floor before any drilling. Original builder plans, when available, show the tendon layout and speed this up considerably. Anchor pockets along the slab edge indicate where cables terminate.

Core holes and pier locations are placed between tendons. Because the pier layout has to work around fixed cable paths, engineers often adjust spacing slightly from the ideal structural layout. This is normal and should be documented on the plan you receive.

If a tendon must be cut, it is de-tensioned first. That is specialized work: the cable is cut in a controlled manner, then re-tensioned and re-anchored after the repair, and the process should be designed and signed off by a structural engineer. Any contractor who talks about simply cutting through a post-tension slab, or who cannot tell you how they locate cables, should not be on your property.

Lifting is done more gradually. A post-tension slab is a single stiff plate held in compression, so it does not tolerate being jacked hard in one area. Crews lift in smaller increments across more points, and the realistic goal is often stabilization plus partial recovery rather than a return to original grade.

The practical takeaways: expect post-tension work to cost more than the equivalent conventional job because of the scanning, engineering, and slower lifting; expect the contractor to produce a marked-up slab plan before drilling; and confirm the engineer’s involvement in writing.

Slab Foundation Repair Cost Factors

Most complete slab projects land somewhere between $3,000 and $25,000, with the majority of typical suburban homes falling in the middle of that band. The variables below explain why two houses on the same street can receive quotes that differ by a factor of three. For pier-by-pier pricing, regional numbers, and how to read a line-item bid, see the full slab foundation repair cost breakdown.

When to Get an Inspection First

A foundation inspection ($200-$750) is recommended before signing any repair contract. An inspector can:

• Confirm the movement is in the foundation (vs. framing, soil shrinkage at finish materials)
• Map the extent of settlement with a laser level
• Identify plumbing leaks that must be addressed first
• Recommend a repair approach without being the one selling the repair

Inspectors who don’t do repair work provide the most unbiased assessment.

What a Complete Slab Repair Quote Includes

A one-page proposal with a lump sum and a promise to “level the foundation” gives you nothing to compare and nothing to enforce. A quote you can actually evaluate contains all of the following.

• The elevation survey data, or at minimum a slab diagram showing measured floor elevations and the low areas the plan is addressing
• Pier count, type, and marked locations on a plan drawing, not a verbal estimate of “around ten piers”
• Target depth or refusal criteria, meaning how the crew determines that a pier has reached capacity: driving pressure for push piers, or installation torque for helical piers
• The stated lift goal, whether the aim is full recovery to grade, partial recovery, or stabilization only, along with the risks of pushing further
• Access details, including which pits are exterior, which piers are interior, what flooring will be cut, and what landscaping is in the path
• Plumbing testing, showing whether a pre-repair leak test is included and what happens to the price and schedule if the test fails
• Restoration scope, spelling out backfill and compaction, concrete patching of core holes, and explicitly whether flooring, drywall, paint, and landscaping are included or excluded
• Schedule and payment terms, with a start window, expected duration, and a payment schedule tied to milestones instead of a large sum demanded upfront
• Engineering involvement, naming the engineer who designed or will sign off on the repair plan if one is involved
• The written warranty document, not a marketing claim on the last page

Get at least three bids built on the same scope. When bids differ wildly, the cause is almost always a different pier count, a different lift goal, or restoration work that one contractor included and another quietly left out.

Warranty Terms That Matter

Most established slab contractors advertise a lifetime transferable warranty on pier work, and the phrase means far less than it sounds like until you read the document. Check four things specifically: what it covers (usually the piers holding their position, rarely cosmetic damage or new movement in unpiered areas), whether it transfers to a buyer and at what fee, what voids it (unaddressed drainage, later plumbing leaks, owner-performed work near the foundation), and who backs it if the company closes. A warranty from a contractor with two years of history is a weaker instrument than the same document from a firm that has operated in your market for twenty. The details of foundation repair warranty terms are worth reviewing before you sign anything.

Contractor Red Flags on Slab Repair Jobs

Slab repair attracts bad actors because the work is expensive, the diagnosis is hard for a homeowner to verify, and fear speeds up decisions. Walk away when you see these patterns.

• A quote written without any measurements. No manometer, no elevation grid, no plan drawing, just a walk-around and a number.
• Same-day pricing pressure. Discounts that expire tonight, or a crew that “happens to be in the neighborhood.” Legitimate contractors hold their bids for weeks.
• Piers recommended before a plumbing test. In a house with damp floors, a rising water bill, or a warm spot in the slab, structural work before leak testing is a guess.
• No mention of tendon scanning on a post-tension slab. If they cannot explain how they locate cables, they are planning to drill blind.
• Large deposits. Asking for 50% or more before any work starts is a common pattern in disputes. Deposits in the range of 10-30% are more typical.
• Refusal to provide license, insurance certificate, or local references. Every one of these is easy for a legitimate contractor to produce on request.
• Guarantees of a perfect lift. Nobody can promise that a slab will return to original grade without cracking finishes or stressing plumbing.
• Dismissing an engineer’s report. A contractor who tells you an independent structural report is unnecessary is protecting their own scope, not your house.

Cross-check any bid against the broader list of foundation repair red flags before you sign. The cost of a second opinion is trivial next to the cost of a wrong repair.

Related Guides

• Slab Foundation Repair Cost
• Slab vs. Pier and Beam Foundation
• Push Piers for Foundation Repair
• Helical Piers
• Foundation Sinking: Causes and Signs
• Foundation Leveling