John Lisle | Updated November 10, 2022 | Foundation Engineering Questions

When I’m talking to an engineer or contractor and they learn I work with helical piers, there’s a common question that tends to come up:

“What’s the big deal about helical piers? We’ve used poured and driven piles with no serious issues. How does a helical pier compare to the solutions we’re already using?”

It’s a fair question. Despite the fact they’ve been around for nearly two-hundred years, helical piers still carry the perception they’re a “new technology”. Engineers and contractors are, rightly so, wary about things that seem “new”.

What we’re dealing with here, really, is a lack of quality information.

Search online for comparisons of foundation technologies and it can be a real mess. You have to sort through poorly-written spam and articles hidden behind subscription windows. No wonder it’s tough to sort it all out.

That’s why I wanted to get back to basics today and do a straightforward summary of the “big four” foundation technologies used in industrial construction today:
● Cast-in-situ concrete piers● Precast driven concrete piers● Steel h-piles● Helical piers

What’s the story behind these foundations, how do they work, and is there one that’s “the best” for your project?

Concrete Piers

Some of the most prolific users (and innovators) of concrete were the Romans, who used it to build mighty feats of ancient engineering like the Colosseum and extensive aqueduct networks.

Concrete was a common building material in the Roman Empire. It's durability as a building material helped structure like the Colosseum stand the test of time

After the Roman Empire fell, humans forgot how to make quality concrete for quite a long time. It wasn’t until about the mid-18th century when concrete was “redeveloped”, grew in popularity, and continued to be refined.
When the industrial revolution arrived and construction grew more mechanized, everything fell into place for the concrete pier. By the early 20th century machines were capable of boring deep into the earth and soon engineers began to use concrete as a deep foundation.
This 1938 catalogue of concrete pier foundations from the Raymond Concrete Pile Company shows us a contemporary look at how concrete foundations were rapidly changing construction in the U.S.

“Raymond piles” were a common foundation for industrial and commercial projects through the early to mid 20th century

Fast-forward to the present day and you can find concrete piers everywhere. Their economy and the availability of raw materials has made them one of the most common deep foundations.

Ignoring all the variants and off-shoots of concrete piers, we can broadly split them into ‘cast-in-situ‘ and ‘pre-cast driven‘.

Cast-in-Situ (Poured Concrete) Piers

“Cast-in-situ” refers to concrete piers that are poured and cured on-site. It’s what’s known as a displacement pier, which means soil needs to be removed from the ground in order to install it.

They offer good capacity and stability, but have some limitations that come as a result of the materials and installation methods.

Installing a Cast-in-Situ Concrete Pier

Exactly how a poured concrete pier is installed will depend on the design of the foundation, site limitations, and other considerations. Again, we’re taking a broad look here and don’t want to get stuck in details.

Here’s how you can, roughly, expect a cast-in-situ concrete pier install to go:
● An excavator or drill rig excavates a borehole for the pie● Spoils are removed from location via trucks● Void forms are installed at the bottom of each borehole. This creates a void space between expansive soils and the foundation, while providing a temporary support formwork for the weight of the concrete until it has reached a specified strength.● Cylindrical casings (tubes) are inserted in the borehole to keep it from collapsing in on itself and to hold the concrete as it cures.● Rebar support cages are manufactured on-site and placed in the casing● Concrete is poured into the casing (if water has infiltrated the form, additional equipment will be needed for pouring)● Casings are removed from the pier and the top is finished off with more poured concrete● Wait up to 2 weeks (or more) for concrete to cure before loads can be applied

Precast Driven Concrete Piers

The precast driven concrete pier is kind of like the cousin of the cast-in-situ pier. Instead of hauling in cement trucks and pouring the pier straight in the ground, precast concrete piers are cast off-site and hauled to site as complete piers. 
This avoids some of the problems with cast-in-situ piers, like long cure times and weather delays.
Precast driven piers tend to be used for heavy-duty industrial and commercial projects due to the space needed to maneuver and install them.

Installing a Precast Driven Concrete Pier

● If soil is especially dense, pre-drilling may be required● A protective steel cap is set on top of the pier to protect it during installation, or there may be a sacrificial section of concrete at the top of the pier designed to be destroyed by the driving process● Piers are loaded on the pier-driving machine and moved into place● The pier-driving machine, usually diesel or hydraulic powered, pounds the pier into the ground● Excess concrete must be carefully trimmed off

Steel H-Piles

If poured concrete takes a long time to cure and precast driven concrete piers are brittle and heavy, then one solution is to find a different material for driven piers.

Steel h-piles are more resistant to damage, easier to handle, and often faster to install when compared to precast driven piers. Their steel construction also makes them easier to trim and, unlike concrete piers, h-piles can be spliced together to increase depth.

Installing a Steel H-Pile

H-piles are manufactured off-site using specified grades of steel
If soil is especially dense, special pilot points may be added to the pile to help drive it into the ground
Piles are loaded onto the pier-driving machine and moved into the correct position
Using diesel or hydraulic power, a pier-driving machines pounds the h-pile into the ground
Pile tops are trimmed to the correct height

H-piles are more versatile than concrete when it comes to splicing and cutting

Helical Piers

Originally called “screw piles”, the helical pier was invented in the early 1830’s by Alexander Mitchell and patented in 1833. 
It was designed for the loose, saturated, sandy soils found along the United Kingdom's countless rivers and coastlines. The poorly-supportive soil made many areas inaccessible to development, and the lack of navigation lights on coastlines was wreaking havoc on maritime transport.

An illustration of the ‘Wyre Light’, one of the first lighthouse projects to be supported on helical piers in 1840

The advent of the helical pier allowed structures to be firmly supported on loose and saturated soils and quickly opened new areas for development.

Helical piers don’t require excavation like cast-in-situ piers and they don’t need to be hammered into the ground like h-piles or precast piers. Instead, they turn into the ground using a hydraulic-powered helical drive head. This drive head can be attached to a range of common equipment like excavators and skidsteers.

An example of a helical drive head attached to a CAT 320E excavator

Installing a Helical Pier

● Helical piers are manufactured off-site to specifications● A skidsteer or excavator attaches the first helical pier section, called the “lead section”, to the helical drive head. The helical drive is attached to a machine with hydraulic power (like an excavator)● After positioning the pier, the helical pier is turned into the ground using the drive head. Torque on the helical pier shaft is monitored to ensure quality of installation and axial capacity.● Pier extensions, which come in standard lengths like 10 or 15ft, are coupled to the lead section that’s already in the ground and then turned-in as well. Extensions are added until the engineering specifications are met● Pier tops are trimmed and topped with the appropriate caps, grillage, or other transition

When speed is key, multiple crews can install helical piers simultaneously to increase efficiency

Summary: Helical Piers vs. Concrete vs. H-Piles

Alright, we’ve looked at each of these foundation technologies on their own. Now it’s time to compare them using a handy infographic we put together. Click on the image to view a larger version of it.
Before we do though, a quick note. The point here is not to try and declare a “winner”. This comparison is intended to help you see the differences between foundation solutions.

Helical Piers vs. Concrete vs. H-Piles

Click the image to view a larger version of the infographic

Conclusion

At the end of the day I can’t tell you what the “perfect” foundation for your project is because, well, I don’t know the specifics of your project. You might see fantastic benefits from using a helical pier foundation, or it might not work for your situation at all.

My point is, you can see every foundation on this list has pro’s and con’s...
● Concrete is relatively affordable and common but can be heavy, awkward, and time consuming. ● H-piles are less hassle than concrete but can be expensive and difficult to install in some locations. ● Helical piers are faster and more versatile but aren’t appropriate for all soil types or situations.

It’s the foundation that will offer the fastest, firmest, most economical support to your project.

To find that foundation, you need to talk to honest foundation experts that have the integrity to help you find the best foundation for your project.

Not just the foundation they sell.

I hope this post cleared up some of the questions you have about the differences between helical piers, concrete piers, and h-piles. If you have more questions about foundations, comments about this article, or want to explore helical piers, scroll down to get in touch with our foundation experts at S&B Helical.