Push Piers vs Helical Piers: What Actually Goes Under Your House

If you have had two foundation companies out, there is a good chance you got two different recommendations, and one of them involved a word you had never heard before last week. Helical. Push. Resistance. Underpinning.

Here is the plain version, written by a company that drives one of these and not the other, so you can decide what is actually right for your house rather than what is right for whoever is standing in your driveway.

Both of them do the same job

Your footing is sitting on soil. The soil moved, so the footing moved, so the house moved. No repair that stays in that soil fixes that.

Both pier systems solve it the same way: they transfer the weight of your house off the soil and onto steel that reaches down to ground that will actually hold. Everything else is a question of how the steel gets down there.

Push piers: a nail

A push pier is a smooth steel tube. We set a bracket under the footing, then hydraulically drive sections of that tube straight down, one after another, using the weight of your house as the thing we push against.

That last part is the whole trick, and it is also the limitation. A push pier does not get driven by a machine's strength. It gets driven by your house's mass resisting the ram. When the tube stops going down, it has found ground dense enough to resist the full weight of the structure above it. That is a useful thing to know at the moment it happens, because the house itself performed the test.

It also means push piers want a heavy building. A full masonry house on a proper footing is the ideal candidate.

Helical piers: a screw

A helical pier is a shaft with steel plates welded on it like the threads of a screw. A machine with a torque motor turns it into the ground until it reaches a specified resistance.

Because a machine supplies the force, a helical pier does not care how much the building above weighs. That is a genuine advantage, and it is why helical piers are the right answer for light structures: porches, decks, sunrooms, additions, and new construction where there is no house there yet to push against.

The tradeoff is that a helical pier stops when the torque reading says stop. Torque correlates with capacity, and it is a real engineering measure, but it is a proxy. A push pier's stopping point is the house's own weight, which is not a proxy for anything.

We drive push piers, and we will tell you when that is wrong

We install driven steel push piers. We do not turn helical piers.

We are telling you that plainly because you should know what a contractor's recommendation is made of. A company that only sells helical will find a reason your house needs helical. We would rather say it straight: if you have a settling front porch, a deck, or a light addition that does not weigh enough to drive against, a helical pier is very likely the better tool, and we will tell you that rather than force our method onto a structure it does not suit.

For the work we do most, which is settled masonry houses, chimneys, and structural slabs across Metro Atlanta, driven steel is the method that fits, and it is what four generations here have gotten good at.

Why Georgia's ground makes depth the real question

Metro Atlanta sits in the Southern Piedmont, and the ground under your house is not one thing. It is a deep column of weathered material sitting on top of hard rock.

The U.S. Geological Survey describes the soils of this region as ultisols, "characterized by sandy or loamy surface horizons and loamy or clayey subsurface horizons," and notes these are "deeply weathered soils derived from underlying acid crystalline and metamorphic rock."^[1] In plain terms: a thick layer of clay and decomposed rock, then granite somewhere underneath it.

The clay layer is the part that causes the trouble, because clay is not stable. Swelling clay "expands or contracts in response to changes in environmental factors," and hydration and dehydration "can vary the thickness of a single clay particle by almost 100 percent." Houses built on soils containing swelling clays "may be subject to structural damage caused by seasonal swelling of the clay portion of the soil."^[2]

So the question that matters in a Georgia yard is not which pier is stronger in a brochure. It is how far down the moving layer goes at your particular house, and whether the pier reaches past it. That depth is not the same in Marietta as it is in Roswell, and it is frequently not the same on two corners of the same house.

Anything that stops inside the clay has not solved the problem. It has joined it.

What this means for your quote

Three practical things fall out of all of this.

The number of piers and their depth set your price, not the pier type. A shallow job needing more piers can cost more than a deep job needing fewer. If someone gives you a per-pier price over the phone, they are guessing at both variables. We wrote about what foundation repair actually costs in Georgia if you want the fuller picture.

Ask what the pier is being driven to, and how they will know. "To bedrock" and "to refusal" and "to torque" are three different claims. Any of them can be correct. A contractor who cannot explain which one applies to your house has not thought about your house.

Ask what happens to the brick afterward. Stabilizing the structure is half the job. Putting the masonry back so the repair is not the first thing you see every time you pull in is the other half, and we do that part in-house.

The honest summary

Push piers and helical piers are both good systems. They are not competing products so much as different tools, and the structure above the ground decides which one belongs under it.

Heavy masonry house that has settled: push piers, driven with the house as the test. Light structure, porch, deck, addition, or new construction: helical, because there is nothing there heavy enough to drive against.

If you are looking at a quote and are not sure which situation you are in, that is exactly what a free inspection is for. Call us at 770-422-2924 or ask for an inspection and we will come look at the actual house. If your answer turns out to be a pier we do not drive, we will say so.

Sources

1. U.S. Geological Survey, "The Apalachicola-Chattahoochee-Flint River NAWQA Program study: Soils" — ga.water.usgs.gov
2. U.S. Geological Survey, "Environmental Characteristics of Clays and Clay Mineral Deposits" — pubs.usgs.gov/info/clays