Foundation Fixers is a Cave Creek crew working Phoenix homes every day. We scan before we cut, we repair to Post-Tensioning Institute (PTI) standards, and we document the work so your insurance file and your future buyer's inspector both have what they need.
What a post-tension slab is
A post-tension slab is a concrete foundation reinforced with high-strength steel cables — called tendons — instead of (or in addition to) a conventional rebar mat. The tendons are pulled tight after the concrete cures and locked into anchors at the slab perimeter, which puts the whole slab into compression.
How PT slabs work
Each tendon is a seven-wire steel strand sheathed in plastic and greased so it can slide. After the concrete reaches strength, a hydraulic jack pulls each tendon to roughly 33,000 pounds of force and a wedge anchor locks it at the edge of the slab. That stored compression keeps the slab from cracking when the soil underneath swells, shrinks, or settles. In other words, the steel is not just sitting in the concrete — it is actively squeezing the slab from edge to edge.
Why AZ builders adopted PT in the 1990s
Phoenix-area soils are rough on foundations. Expansive clay swells when wet and shrinks when dry, caliche layers are unforgiving, and the monsoon season cycles moisture in and out every summer. A conventional rebar mat slab handles that movement poorly. A post-tensioned slab handles it well because the built-in compression resists the tensile stress that cracks slabs apart. PT slabs are also cheaper to pour and faster to build than a thicker rebar-mat slab — which is why almost every tract home built in the Valley since the early 1990s sits on one. For the soil side of this, see why Arizona soil moves.
How to tell if your house has a post-tension foundation
Most homeowners do not know what kind of slab they have until something goes wrong. Three quick checks:
- Cable-end "dimples" around the perimeter. Walk the outside of your house and look at the edge of the slab where it meets the stucco. On a PT slab you will see small round patches — usually quarter- or half-dollar sized — spaced every 4 to 6 feet around the entire perimeter. Mortar plugs covering the cable-end anchors.
- Plans or city building records. Original blueprints will call out a "post-tensioned slab" or show tendon layouts. If you do not have the plans, the city building department keeps the permit records.
- Era and neighborhood. Tract homes from roughly 1990 onward — Anthem, Surprise, Goodyear, Buckeye, Queen Creek, San Tan Valley, parts of Maricopa, newer Scottsdale and North Phoenix builds — are almost certainly post-tensioned.
Signs of post-tension trouble
- Diagonal slab cracks wider than 1/8 inch, especially ones that are growing month to month
- A sudden loud bang or "pop" from the floor — often the sound of a tendon snapping
- Doors that suddenly will not latch, or fresh drywall cracks above door frames and window corners
- Bulging tile, lifted vinyl plank, or popped grout lines following a straight line across a room
- Plumbing leaks weeping up through slab cracks — a leak can both cause and reveal PT damage
Any one is worth a call. Two or more together means a scan now, not next month. More early warning signs in the blog.
Why post-tension repair is different
This is the part most general contractors get wrong, and it is the reason we wrote this page.
You cannot just patch the crack
On a conventional slab, a crack is mostly cosmetic and a moisture-intrusion problem. You grind it, fill it with epoxy, and move on. On a PT slab the crack is a symptom — the load path lives in the tendons running underneath. If a tendon is broken or de-tensioned, the slab has lost compression in that zone and the crack will keep coming back, wider every season.
A failed tendon has to be repaired, not ignored
The fix is a defined sequence: locate the cable, expose the anchor, de-tension what is left, splice in a coupling or replace the strand, and re-tension to the engineer-specified force with a calibrated jack. Done right, the slab goes back into compression and the crack stops moving.
Lift and leveling are different on a PT slab
Polyurethane foam injection is the right tool for lifting a settled PT slab, but the injection pattern has to be planned around the tendon layout. Foam pumped under the wrong spot can deflect a cable, change the load path, and create a new problem while fixing the old one. We use GPR to map every tendon before we drill the first injection port.
Our post-tension repair process
- GPR scan. Ground-penetrating radar across the affected area maps every tendon, anchor, and embed before we touch the slab. No guesswork, no struck cables.
- Crack mapping. Chalk-line the crack pattern, measure widths, and shoot the slab with a laser level to know exactly how much movement we are dealing with.
- Broken-tendon repair. Expose end anchor, de-tension the remaining strand, splice in a PTI-compliant coupling (or replace the strand), re-tension to the engineer-specified force.
- Settlement lift. Inject high-density polyurethane foam at planned points between tendons, monitoring lift in real time until the slab is back in plane.
- Patch and finish. Crack repair with structural epoxy, anchor pockets sealed with non-shrink grout, clean restoration so your finish floor goes back over.
Every PT repair we do is permitted, signed off by a licensed structural engineer of record, and backed by our transferable warranty. You get a written scope, a written quote, and a closeout packet with the GPR map, tendon force readings, and engineer's letter — the documents your insurance carrier and your future buyer will both ask for.
What post-tension slab repair costs in Phoenix
PT pricing is not one number, because there are three different jobs hiding inside the phrase "post-tension repair":
The GPR scan itself is a fixed line item, and it is non-negotiable on every PT job we quote. A scan that costs a few hundred dollars protects a slab worth tens of thousands. Call (602) 833-4600 or request a written PT assessment for tier-specific pricing on your job.
Why this work requires a specialist
A general slab contractor can grind and fill a crack. Only a post-tension specialist can safely re-tension a cable, and the distinction matters more than most homeowners realize. The wrong fix on a PT slab does not just fail — it actively gets worse. A crack-fill over a broken tendon hides the symptom while the underlying compression loss keeps spreading load to neighboring tendons. Eventually a second one fails, then a third, and now you are looking at a multi-tendon job instead of a single-tendon repair.
Insurance and resale both care about how the work was done. Carriers want documentation that the repair followed PTI standards. Inspectors at resale want to see permits, engineer sign-off, and the GPR map showing what was found and fixed. For homeowners weighing bigger options, our repair vs. replacement guide walks through when a PT repair is the right call.