The short answer
Slab repair on Collin County clay usually means underpinning: piers placed under the slab’s beams where it has dropped, then a careful lift. The Texas Section of the American Society of Civil Engineers (ASCE) lists the full set of slab repair methods as underpinning, grouting, mudjacking, crack injecting, tendon stressing, and partial demolition and reconstruction. Piers are the workhorse; the others fill narrower roles.
It matters here because slabs are the norm. ASCE Texas says most foundations built in Texas are shallow, stiffened slab-on-ground foundations, many of them on expansive clay. In McKinney, 73% of homes date from 2000 or later.
How a slab moves on this clay
A slab doesn’t sink evenly like a boat. It bends, because the clay under its edges dries and wets faster than the clay under its middle. Houston black clay covers more of Collin County than any other soil, and its shrink-swell potential is rated high. Under parts of McKinney and Frisco sits Eagle Ford shale, which a 2022 presentation by McKinney’s engineering director rated high for expansive movement.
| Pattern | What you see | Usual cause | Usual fix |
|---|---|---|---|
| Edge or corner drop | Stair-step brick cracks, doors near outside walls sticking | Clay drying under the perimeter: drought, trees, poor watering | Exterior piers along the low edge, then a lift |
| Center heave | Interior drywall cracks, a hump in the middle, doors in the center binding | Water reaching the clay under the slab: a leak or a wet season | Find and stop the water first. Piers alone don’t fix heave |
| Tilt | One side of the house lower across its whole length | One side drying or settling more than the other | Piers along the low side |
The heave row is the one people get wrong. The Foundation Performance Association says repair piers will not prevent foundation uplift unless they are designed to do so. Lifting the low edge of a heaved slab to match a high middle can mean raising the whole house, so a leak test and an honest diagnosis come before any pier plan.
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Slab repair methods compared
| Method | What it does | When it fits | Limits |
|---|---|---|---|
| Piers (underpinning) | Transfers the slab’s weight to deeper soil or rock, then lifts it | Settlement at edges or corners | Only supports the area piered |
| Mudjacking or foam | Pumps grout or foam under the slab to lift and fill voids | Small, shallow lifts; flatwork | FPA calls it a shallow repair system; it moves with the soil |
| Crack injection | Fills slab cracks with epoxy to restore stiffness | Cracks in a slab that has otherwise stopped moving | Doesn’t lift or support anything |
| Tendon stressing | Restores tension in a post-tensioned slab’s cables | Tests show the tendons have relaxed | Only for post-tensioned slabs |
HomeAdvisor puts slabjacking at $500–$1,300, far below a pier job, which is why it gets offered. On active clay it’s usually a patio or driveway fix, not a house fix. The pier types guide compares pressed concrete, steel, helical and drilled piers in detail.
Exterior and interior piers
Exterior piers go in from outside. The contractor digs a hole beside the perimeter beam at each pier spot, installs the pier, sets a jack and lifts, then shims or blocks the beam onto the pier and backfills. Landscaping along that wall gets disturbed; ask who restores it.
Interior piers support beams under the middle of the slab. Reaching them means cutting through the floor inside the house or tunneling under it from outside. Either way it costs more per pier and touches flooring, so a plan with interior piers should say why the middle needs support.
Partial repairs. Many plans pier only the area that dropped. That’s normal, with one caveat from ASCE Texas: the repair documents should state that underpinning will not improve the performance of the foundation in non-underpinned areas. If the unpiered side moves next year, that isn’t a failure of the piers. It’s the limit of a partial repair, and it’s worth understanding before you choose one.
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The lift and the plumbing under the slab
Lifting a slab flexes the pipes cast under it. ASCE Texas says water supply and drain lines should be tested for leaks whenever jacking or lifting is part of the repair, and leaks found should be fixed. Under-slab plumbing repair is licensed work in Texas. Ask whether the test happens before the lift, after it, or both, and who pays if it finds a leak.
Leaks found this way aren’t rare, and they’re one reason quotes differ. Fixr puts an average slab leak repair at $2,500, covering detection, tunneling and patching. If a leak caused the movement, read the insurance guide: sudden plumbing leaks are the main foundation exception in Texas policies.
Then there’s the lift itself. ASCE Texas calls it unlikely that lifting will leave a foundation level, and recommends lifts be governed by field judgment to limit damage to the house. A careful contractor stops short of forcing the last fraction of an inch if the brick or drywall is protesting. The house leveling page covers what to expect.
What slab repair costs
| Item | Typical cost | Source |
|---|---|---|
| Slab repair, by damage | $1,000–$10,000 | HomeGuide |
| Piers, per pier | $1,000–$3,000 per pier | HomeAdvisor |
| Piers on a typical slab job | 5–15 piers | Olshan (contractor figure) |
| Steel push piers, per pier | $990–$1,350 per pier | Olshan (contractor figure) |
| Drilled concrete piers, per pier | $765–$1,100 per pier | Olshan (contractor figure) |
| Slab leak repair, average | $2,500 | Fixr |
The cost page explains why two quotes for one slab can differ by several piers.
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McKinney’s permit
McKinney counts leveling and pier work as foundation repair, so a slab job needs a city permit, an engineer’s letter and drawings before the permit is issued, and a final engineer’s report to close it. Frisco and Plano also want an engineer on the permit. The permit guide sets out each city’s rule, and the Frisco page covers that city’s stamped pier drawings.
After the repair
- Expect improvement, not perfection. ASCE Texas puts it plainly: perfection is not attainable by remedial measures.
- Fix the water. The Foundation Performance Association warns that improper drainage can cause continued movement to the repaired slab. Gutters, grading and steady soil moisture protect the piers you paid for. See drainage and soil moisture.
- Get the after-repair readings. ASCE Texas says floor elevations should be re-measured once the work is done, with the record given to the owner.
- Keep the file. Permit, engineer’s letter, final report, pier drawing, plumbing test results and warranty. A buyer will ask for all of it.
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Before you sign a slab repair plan
- Does the plan match the elevation survey, and can I have a copy of both?
- Which piers are exterior and which interior, and why are the interior ones needed?
- What pier type, to what depth or pressure, and will I get the installation records?
- Is a plumbing test included, before or after the lift, and who repairs a leak if one turns up?
- Who pulls the McKinney permit and provides the engineer’s letter and final report?
- What does the warranty cover, does it pass to a buyer, and what would void it?
Get at least two written plans for a pier job. Work is done by independent local contractors. Pricing and availability are set by the contractor serving your area.