The short answer
Every common pier type can work on Collin County clay, and every one can fail if it’s installed too shallow, spaced too far apart or set under a house whose drainage keeps the soil swinging. The type matters less than three things: how deep it goes, how the plan places it, and what keeps the clay around it steady afterward.
The four pier types side by side
| Pier type | How it’s installed | What holds it up | Typical price per pier | What to watch for |
|---|---|---|---|---|
| Pressed concrete pile | Precast concrete cylinders stacked and pressed into the ground with the house’s weight as resistance | skin friction along the side of the pile | About $1,000 per pier (Angi) | Stopping shallow, inside the soil that moves |
| Steel push pier | Steel pipe sections pressed down with the house’s weight, toward rock or firm strata | Friction along the pipe, or end bearing if it reaches rock | $990–$1,350 per pier (Olshan, contractor); about $2,000 per pier (Angi) | Not reaching refusal; bending if pushed off angle |
| Helical pier | Steel shaft with screw plates turned into the soil by hydraulic equipment | The helix plates, at the required torque | $2,000–$4,000 per pier (HomeGuide) | Spacing, angle, and the bracket connection to the beam |
| Drilled concrete pier | A hole drilled to depth, reinforced with steel and filled with concrete | the bottom of the pier, plus some side friction | $765–$1,100 per pier (Olshan, contractor) | Depth, a sound base, and water getting down the shaft |
The descriptions and cautions come from the Foundation Performance Association’s paper on post-repair performance, written by a committee of Houston engineers about expansive clay much like ours.
Pressed concrete piles
Short precast concrete cylinders are pressed into the ground one on top of another, using the house as the weight, until the pile stops going down and the house starts to rise. Most of the support comes from skin friction along the side of the pile. They’re common and usually the cheapest option per pier.
The risk is depth. The FPA warns that shallow piling not driven sufficiently below the moisture active zone can continue to settle as seasonal moisture changes occur, and that drought can cause skin friction to release at shallow depths. Ask how deep the piles typically reach on your street, and whether each segment is reinforced with a central cable or bar.
Steel push piers
Steel pipe is pushed down in sections with the same house-as-weight method, usually until it hits refusal: rock or a layer firm enough to stop it. Steel generally reaches deeper than pressed concrete, which is its main selling point on clay. The FPA’s caution: a pipe pile that isn’t pushed to refusal may move as the seasons change, and one pushed off vertical can bend under load. Ask for the depth and final pressure recorded at each pier.
Helical piers
A helical pier is a steel shaft with one or more screw plates, turned into the ground like a screw until it reaches the required torque, which correlates with how much load it can carry. A bracket then transfers the house’s weight to the pier. Helical piers can work where the house is too light to push piers deep, and they’re among the pricier options: HomeGuide lists $2,000–$4,000 per pier, and Angi averages about $3,000 per pier.
Drilled concrete piers
A hole is drilled, steel goes in and concrete is poured, sometimes with a bell flared at the bottom. Support comes mainly from the bottom of the pier. Drilled piers don’t rely on the house’s weight to install, so they suit lighter structures. Their weak points are depth, loose material left in the bottom of the hole, and gaps around the shaft that let water reach the clay below.
How many piers, and how to check a count
Pier counts follow the part of the foundation that moved, not the size of the house. Angi says contractors use about 10 piers on average; Olshan says most slab jobs need 5–15 piers. A rough check: measure the length of foundation beam that has dropped, divide by the spacing the design calls for, and add one.
Example: if the elevation survey shows 40 feet of perimeter beam has settled and the design spaces piers about 6 feet apart, that’s roughly 7 to 8 piers, plus any at a corner.
If two plans for the same house differ by several piers, ask each contractor to show the low readings each pier answers to.
Where the chalk is shallow
Across much of Collin County the clay sits on marl and chalk, and the depth to firm material varies. In parts of Allen, the USDA’s 1930 survey found hard white chalk only 10 to 24 inches below the surface; elsewhere the clay runs much deeper. Frisco’s engineering standards treat local subgrades as either Eagle Ford shale or Austin chalk. Where firm material is close, a shorter pier may reach it; where the clay is deep, depth is the whole question.
What matters more than pier type
- Depth below the active zone. Every type in the FPA’s list can settle if it stops in soil that still shrinks and swells.
- Drainage after the repair. The FPA says improper drainage can cause continued movement to the repaired slab. Piers don’t make the clay stop moving; they put the house’s weight below the part that moves most.
- Heave. Repair piers will not prevent foundation uplift unless they are designed to do so. If the middle of the slab is rising, more piers at the edge won’t fix it.
- The design and who stands behind it. In McKinney, Frisco and Plano, an engineer’s letter or sealed drawings come with the permit. ASCE Texas calls the engineer who seals the repair documents the engineer of record.
- Records. Depth and pressure or torque at each pier, plus after-repair elevations. ASCE Texas says floor elevations should be re-measured after the repair, with a copy to the homeowner.
- The warranty terms. What it covers, whether it includes re-leveling, what voids it, and whether it transfers to a buyer.
The slab repair page explains how piers fit into a full repair, and the cost page shows how pier type and count drive a quote.
Want a contractor to look at it? Call to schedule an inspection.