Post-Tension Slab Repair: What Makes It Different

Post-Tension Slab Repair: What Makes It Different

If your home sits on a post-tension slab, foundation repair is a different conversation than it is for a conventional slab — different risks, different methods, and different questions to ask. Here is what changes and why.

What makes post-tension slab repair different? Post-tension slabs contain steel cables tensioned to thousands of pounds of force inside the concrete. Cutting or drilling into one without knowing where those cables run can snap a tendon and seriously weaken the slab, so post-tension slab foundation repair requires cable locating, specialized methods, and a contractor who has done this specific work before.

Most homeowners have no idea what kind of slab they have until something goes wrong — a crack spreading across the garage, a corner of the living room sitting a little low — and someone mentions “post-tension.” Suddenly a routine repair comes with warnings about cables under tension. It sounds intimidating, but it is straightforward as long as the person doing the work understands what is in the concrete.

In this guide: what a post-tension slab is, why repairs follow different rules, which methods work, what it costs around Shreveport, and how to spot a contractor who actually knows post-tension. Our expansive clay — swelling after soaks like the early-October rains, shrinking in dry stretches like the one we are in now — is exactly the soil these slabs were designed for.

What a Post-Tension Slab Actually Is

A conventional slab gets its strength from rebar sitting passively in the concrete. A post-tension slab works differently: steel cables — tendons — run through plastic sheathing in a grid, and after the concrete cures they are pulled tight with hydraulic jacks and anchored at the slab edges. That built-in squeeze plays to concrete’s strength — strong in compression, weak in tension — making the slab far more crack-resistant than a conventional one.

The design exists for moving soil. Post-tension slabs were developed for expansive clay — exactly what sits under northwest Louisiana. When our clay swells after heavy rain or shrinks in a dry spell like the rain-free stretch Shreveport is in through October 29, a conventional slab cracks along with the movement; a post-tension slab rides it out because the cables hold everything in compression. That is why builders across Shreveport, Bossier City, and Blanchard embraced them from the 1980s onward.

You can often spot one yourself: look for small patched rectangles or plastic caps along the slab edge — those cover the anchor pockets — or a warning stamp on the garage floor or electrical panel reading “post-tension slab — do not cut or drill.” If you are buying in South Highlands or Broadmoor and the disclosure mentions post-tension, find that stamp before anyone works on the slab.

The key fact: the cables are the slab’s strength. Cutting a tensioned tendon releases all that stored energy at once — the cable can whip, concrete can blow out, and the slab loses real structural capacity. Tendon strikes injure workers every year. That single fact makes post-tension slab foundation repair a specialty job.

Why Repairing a Post-Tension Slab Is a Different Job

On a conventional slab, a contractor can drill, excavate, and cut freely. On a post-tension slab, every step gets a constraint:

• Every penetration must be mapped first. Before a drill bit touches the slab — for foam injection, pier brackets, or plumbing — the cable layout gets located with ground-penetrating radar or a pachometer. Drawings help, but cables can deviate from them, so scanning is the standard.
• You cannot just cut an opening. Saw-cutting for interior piers or plumbing means working around tendons. A contractor who treats it like a regular slab cut is a contractor to dismiss.
• Lifting must be gentle and even. Post-tension slabs are thinner and more rigid. Aggressive, uneven lifting can crack the slab or overload cables — the lift has to be slow, monitored, and distributed.
• Edge work avoids the anchors. The anchor pockets along the slab perimeter are the most sensitive spots on the foundation. Exterior underpinning brackets must be placed to avoid disturbing them.
• Crack repair has limits. Hairline cracks are often just the slab doing its job. A crack that keeps widening, or one with vertical displacement, means the slab is moving as a unit — a settlement problem, not a cable problem.

A good contractor treats the cable layout like buried utilities: locate before you drill, every time, no exceptions.

How Post-Tension Slab Repair Is Actually Done

Once the cables are mapped, repair uses the same method family as conventional slabs — with a post-tension adjustment to each:

Polyurethane foam lifting is the most common fix. Small holes are drilled between the cables (never through them), and expanding foam fills the voids and lifts the slab back toward level. The holes are tiny, the foam adds almost no weight to our soft clay, and the process suits the thinner post-tension profile. For typical 1–2 inch settlement, foam is usually the first recommendation.

Exterior piers handle deeper or still-active settlement. Steel push piers or helical piers go around the perimeter, brackets placed to avoid anchor pockets — interior piers are far more involved on post-tension, so most jobs stay outside. See our slab foundation repair page for how we match method to slab.

Mudjacking is possible but rarely the best choice here: heavy slurry, bigger holes (more chances to conflict with cable runs), and our clay dislikes the extra weight. Most experienced local contractors have moved to foam for surface lifts.

Crack injection seals non-structural cracks against water — straightforward unless there is displacement (one side higher), which signals independent movement needing a structural fix. More on the decision in our guide to whether a slab foundation can be repaired.

Cable re-tensioning is unique to post-tension: if an inspection finds a tendon that has lost tension — sometimes visible as a loose anchor at the slab edge — a specialist can sometimes re-stress it. Rare work, but the option exists.

Warning Signs Your Post-Tension Slab Needs Attention

Post-tension slabs crack less than conventional slabs, so when symptoms show up, take them seriously — roughly in order of urgency:

• Cracks wider than a quarter inch, especially ones that keep growing month to month. Hairline shrinkage cracks are normal; widening cracks are not.
• Vertical displacement at a crack — run your hand across it. If one side sits higher, the slab is moving differentially: the clearest sign of settlement.
• Doors and windows sticking on one side of the house, getting worse over time. The slab is tilting and the frames are racking with it.
• Sloping floors you can feel. Set a marble on the floor in a few rooms. If it consistently rolls the same direction, the slab has taken a tilt.
• Gaps at baseboards or where floor meets wall, especially along exterior walls.
• Damaged anchor pockets along the slab edge — cracked concrete around an anchor, or a cable end that looks corroded or loose. Post-tension-specific; worth a professional look promptly.
• Water pooling against the foundation after rain. It does not hurt the cables directly, but saturated soil is what moves the slab.

One reassurance: a post-tension slab with a few hairline cracks and no other symptoms is usually fine — the cables are doing their job. Widening, displacing, or multiplying cracks mean the soil has shifted more than the design can absorb.

What Post-Tension Slab Repair Costs in Shreveport

Post-tension work costs more than the same repair on a conventional slab — you are paying for cable locating, planning, and a slower pace. Honest ranges for our market:

Repair type	Typical Shreveport range	When it applies
Cable locating / engineering review	$300–$800	Before any drilling or cutting
Crack injection (non-structural)	$300–$900 per crack	Sealing stable, non-structural cracks
Foam lifting (polyurethane)	$1,500–$6,000	1–2 inch settlement, room or garage
Exterior pier underpinning	$1,200–$3,000 per pier	Deep/active settlement; 8–15 piers typical
Cable re-tensioning	$1,000–$2,500 per tendon	Only when a tendon lost tension

A straightforward foam lift on an accessible garage bay lands near the bottom of its range; a pier job on a two-story brick home with limited access and deep clay lands near the top. Drainage corrections — gutters, grading, a French drain — are often quoted alongside the structural work, because fixing the slab without fixing the water that moved it is a repair with an expiration date. For more local pricing detail, see our slab foundation repair cost guide for Shreveport.

The cheapest quote is rarely the best value on post-tension work. If a bid skips cable locating entirely, or prices the job like a conventional slab with no mention of tendons, that contractor is planning to wing it. The savings are not worth the risk — to your slab or the crew holding the drill.

Post-Tension Myths Worth Clearing Up

Plenty of confident nonsense circulates about post-tension slabs. Cleared up:

• “You can never drill into a post-tension slab.” Not true — you drill into them all the time, but only after locating the cables and only in the safe zones between them. “Never drill blind” is the real rule.
• “Post-tension slabs never settle.” They settle less and crack less, but they sit on the same Shreveport clay as everything else. Severe moisture swings, plumbing leaks, and poor drainage move them too.
• “A cracked post-tension slab is ruined.” Hairline cracks are normal and expected; even wider cracks are usually repairable. Real trouble — severed tendons or failed anchors — is uncommon.

The Post-Tensioning Institute publishes the industry standards for this work — a contractor who references PTI guidelines is speaking the right language. For the engineering side of why our soils move, the Utah Geological Survey’s problem-soils guide describes our Shreveport clay to a tee.

Questions to Ask Before You Hire for Post-Tension Work

Post-tension slab foundation repair is one of those jobs where the estimate meeting tells you almost everything. Bring these questions:

• How do you locate the cables before drilling? You want to hear “ground-penetrating radar” or “pachometer scan” — not “we go by the drawings.”
• How many post-tension slabs have you repaired? A number, not a vibe. “Plenty” is not an answer.
• Will you lift with foam or piers, and why? The answer should reference settlement depth, whether movement is active, and the slab’s condition — not just the equipment they own.
• What are you doing about water? Drainage, gutters, grading — if the estimate ignores the moisture that moved your slab, the repair is fighting the same battle twice.
• What does the warranty cover, exactly? Get it in writing: length, coverage, exclusions. We offer a 20-year structural warranty on qualifying repairs.
• Can I see the cable layout you mapped? A contractor who scanned your slab should be able to show you the tendon map. Ask to see it.

A post-tension slab is good engineering, and repairing one is straightforward for a crew that respects it. Trouble starts with the cheapest bid hired without these questions, or a handyman drilling “just one hole.” If your slab shows warning signs, start with a free foundation inspection from a team that maps cables before it drills.

Frequently Asked Questions About Post-Tension Slab Repair

Can a post-tension slab be repaired?

Yes — foam lifting, exterior piers, crack injection, and occasionally cable re-tensioning. The methods are established; they just require cable locating before any drilling or cutting.

Is it dangerous to drill into a post-tension slab?

Drilling blind is dangerous — striking a tensioned tendon can injure workers and damage the slab. Drilling after cable locating, in the safe zones between tendons, is standard practice done every day. The danger is skipping the locating step, not the drilling itself.

How much does post-tension slab repair cost in Shreveport?

Foam lifting typically runs $1,500–$6,000, exterior piers $1,200–$3,000 per pier, crack injection $300–$900 per crack, and cable locating $300–$800 if billed separately. The premium over conventional slab work covers the scanning and extra care.

How do I know if my home has a post-tension slab?

Look for small patched rectangles or caps along the slab edge (anchor pockets), a warning stamp on the garage floor or electrical panel, or check your disclosure documents. Homes built from the 1980s onward are the most likely candidates; a contractor can confirm it during an inspection.

Can you install piers on a post-tension slab?

Yes, usually on the exterior — steel push or helical piers around the perimeter, with brackets placed to avoid the anchor pockets. Interior piers mean cutting around tendons, so most post-tension pier jobs stay outside.

Does post-tension slab repair come with a warranty?

Yes — reputable contractors warranty post-tension work like conventional work. We offer a 20-year structural warranty on qualifying repairs. Get it in writing: length, coverage, exclusions, and whether the post-tension-specific aspects are covered.

Pelican Foundation Repair
6118 Fairfield Ave, Shreveport, LA 71106, USA
318-585-2003
https://foundationrepairshreveport.com/