John Lisle | Updated December 23, 2022 | Helical Pier Foundation Engineering

Previously on our S&B Helical Blog, we looked at how much a helical pier foundation can cost you in the USA. What we found is there's many different design factors that will determine the cost of your foundation, like your soil conditions and the structure you're supporting.

One of the key factors that makes a big impact on the cost of your foundation is how many helical piers your foundation requires. If you need more helical piers, it (generally) increases the cost of your foundation.

When it comes to industrial projects like oil, gas, renewables, or infrastructure, your margins are thin and maximizing your budget is key. Even a 5% increase in the amount of helical piers you need could have a noticeable effect on your budget. That's why it's so critical your helical pier foundation is value-engineered for maximum efficiency and economy.

But, how exactly do helical pier engineers design a rock-solid foundation that's also hyper-efficient when it comes to budget? 
That's the magic of helical piers, and if you read this post you might save your project a bundle of time and money.

Helical Pier Foundation Design Actually Starts With You

Technically, foundation design starts with your project, but I thought it sounded catchier to say it started with you. In any case, before our foundation engineers can do anything, they'll need to learn everything there is to know about your project. 
These are called "design considerations" and they help provide us with a more complete understanding of your needs. 

Before we could install this slug catcher foundation, we had to consider all aspects of the project first

No two building projects will ever be exactly the same. You could build two completely identical structures right next to each other and still face dramatically different soil conditions. That's always been one of the challenges with deep foundations. No one can be totally certain about what's happening in the soil 30, 50, or 100 feet below the surface. 
(By the way, that's why reliable geotechnical reports are so critical to your project. They're your best tool for understanding the soil conditions on your site as much as possible. The more you know about your soil, the better equipped you are to make wise decisions.)
Doing good "ground work" at this phase is guaranteed to help save you migraines later on. You might not be able to avoid all of them, but you can dodge more than a few. I'll give you an example...
We handled a project where a customer came to us after their original helical contractor provided an over-engineered design. Our team identified areas to increase efficiency by paying close attention to the design considerations. 
In the end, we saved the customer over $300,000 off the price our competitor had offered by following the design considerations to engineer a more efficient foundation. 

These are just some of the considerations our engineers keep in mind when designing the foundation for your project

A quality contractor will want to know as much about your project as possible, especially when it comes to data about your soil conditions. It's only the under-trained, inexperienced, or lazy contractors, who don't care to spend enough time gathering information to help inform the foundation design.

Putting in the extra effort at this key phase will deliver dividends later.

Designing an Efficient Helical Pier Foundation

After our engineers and foundation designers have all the information about your project, they can transform that raw info into a function foundation design. In a way it's kind of like cooking a delicious hamburger, let's say. We know the ingredients we need and have an established process to follow, but we can make tweaks as needed in order to perfect the meal.

Helical pier design is like that, too.

Our engineers know the ingredients they need and they have a process to follow. The technical artistry comes in as our design teams tweak each ingredient to perfection in order to produce a perfect dish.

There's many components that can be tweaked on a helical pier to achieve different performance characteristics

(Maybe I shouldn't write blog posts when I'm hungry)

Using the data we gathered we can begin to work out the configuration, size, and number, of helical piers you're going to need. Like a chef developing a recipe, they'll start with a solid base and then make refinements.
(Okay, no more food analogies)

There's a boat-load of things a designer can adjust on a helical pier to achieve the desired performance. Initially, I was going to try and cover as many of them as I could. Then I realized that would make this post thousands of words long and not very exciting to read.

Instead, we'll study two key design considerations that have a significant influence on the design and cost of your foundation.

Two Key Ingredients for an Industrial Helical Pier Foundation

Structural Load Type

Your structure can face different types of loads depending on its design, location, local climate, soil conditions, and more. Figuring out what these loads are for your structure is one of the first steps to designing a solid foundation.
The two primary structural loads your project will face are axial loads and lateral loads.
Axial loads are exerted in a vertical direction. These loads can be either compression (pushing down) or tension (pulling up). Picture pushing a stick straight down into the dirt - that's a compression axial force. If you pull that stick straight out of the ground, you're exerting a tension axial force. 
In foundation engineering axial loads tend to come either from the weight of the structure pushing down (compressive load) on the helical pier, or from forces exerted on the structure that cause it to pull up (tension load).

This liquid tank will exert enormous axial loads on the foundation, so resistance to compression forces is critical

Lateral loads are exerted in a horizontal direction. Like axial loads these can be in compression or tension. However, the design tactics used to defend against high lateral loads are different than those for high axial loads.

Take a tall and narrow structure like a natural gas flare in a compressor station, for example. As the wind blows on one side of the tower it exerts lateral force on the structure. This force will cause the foundation on one side of the structure to experience increased tension loads, but the other side will see increased compression loads. 
Loads like these can be more challenging to overcome and so may increase the complexity (and cost) of your foundation.

Tall and narrow structures tend to exert lateral loads on the foundation

What type of loads your structure will experience is just as important as how much they'll experience. Helical piers are more than capable of tackling high axial and lateral loads, whether in compression or tension. The trick is to make sure the foundation designers closely understand the indicated loads.

This is serious stuff, too. It's not just about saving you money, it's about the safety of your project.

I've seen cases where helical piers failed because the original installer didn't understand the structural loads. Lateral loads ended up being much higher than anticipated and, over the years, the piers steadily shifted. By the time we saw it, the foundation needed serious underpinning and repair.

Situations like that aren't the fault of helical piers. They're the fault of designers who didn't understand the project and installers who didn't understand the installation criteria per the design, site conditions, or helical technology.

Make sure your contractor cares about understanding every aspect of your project.

Soil Characteristics

It's not unreasonable to say that soil characteristics are the single biggest factor that influences the design of your foundation. Working as a foundation contractor has made me appreciate just how complex and incredible the soil beneath our feet really is. 

Each layer of soil will interact with your deep foundation in a unique way, and will affect the final design of your foundation

Now, the first thing you need to know about soil characteristics is that, at the end of the day, no one can tell you with 100% certainty what's underground. Using the latest in geotechnical investigations, though, we can get a pretty strong idea of the conditions we'll face. That's important, because flying blind on a deep foundation design and install would be a profoundly bad idea.

Let me illustrate what I mean with a couple examples.

Let's say your building a structure on a site with loose and poorly consolidated soil. Depending on your structural loads, this soil may need a larger diameter helical pier that has wider helix plates. We might also add additional helix plates to the helical pier to increase capacity. More surface area equals more resistance to movement, even in very loose soil.

On the other hand, you might get lucky and have dense and consolidated clay soil with outstanding characteristics. In this soil you could likely achieve the same results as the loose soil, but with smaller (or fewer) helical piers.

This example also illustrates how you could have two identical structures with very different foundation designs. Supporting axial compression loads in dense clay will require a different design compared to that same load in sandy soil.

This is why I go on and on about having great geotechnical reports for your jobsite. Quality geotech is the lifeblood of a dependable helical pier foundation. They may not be infallible, but these reports give you a vital insight into the likely conditions underground. The report can tell us about the layers of soil to expect, the depth and thickness of those layers, bearing capacity, water drainage, expansiveness, and a lot more.

Every one of those points of data ends up in the hands of our engineers, who scrutinize it and incorporate it into the foundation design.

If your foundation contractor doesn't emphasize geotech work, that's a warning flag. Diving into designing a helical pier foundation without studying a professional geotech report is like trying to drive a car with your eyes closed.

You'll have no idea where you're going, what you're doing, and it's probably going to end in disaster.

How to Customize a Helical Pier Foundation

Helical pier engineers will study more design considerations than the two we looked at, but they should give you an idea of how comprehensive the whole process is. We don't rely on guesswork or gut feelings to engineer an industrial helical pier foundation. Everything from design to installation is guided by hard data and clear procedures.

In fact, it's the relationship between data and design that makes helical pier foundations so adaptable.

Once upon a time, engineers only had a couple options to customize a helical pier: increase the diameter or increase the length. The manufacturing and installation technology of the era didn't allow them to do much more than that. 

Helical piers were a revolutionary invention, but engineers of the day were fairly limited in terms of custom-designing a helical pier

To be fair, those engineers of old still designed helical pier foundations that would stand for more than a century. Good engineering is good engineering, regardless of the specific technology you have available to you.

These days our engineers are practically spoiled compared to their 1800's counterparts. Designers can customize everything from the thickness of the steel to the number of helices welded to the shaft. We can add protective coatings like galvanization or use hardier grades of steel for extra durability. To top it all off, the entire foundation can be simulated and tested on a computer before crews ever arrive at your jobsite.

Pretty mind-blowing stuff if you're an 1800's helical foundation engineer, but it's all standard practice among quality foundation contractors.

All this fine-grained control results in a better foundation for your project. No waste, no excess material, no unnecessary piers in the ground. There's a real beauty in a tightly-engineered foundation, even if no one will ever see it after it's installed.

So, even though there's no "one size fits all" helical pier foundation, that's a very good thing. It means you can get precisely the foundation you need, because it's designed for the demands of your specific design considerations. Remember that time might equal money, but increasing efficiency can give you more time.

Are Helical Piers a More Affordable Foundation?

Another way to ask this question would be "are helical piers cheaper than poured or driven piers?"

Yes.

And... no.

First, what I'm saying with this talk about engineering and design is this:

Installing an efficient, effective, and economical helical pier foundation for your project doesn't happen by accident. It's the result of enormous amounts of skill, attention, effort, and technology. You know how it goes by now - no guesswork, no gut feelings. 
Outstanding foundations are built on hard data.

This lighthouse in the U.S. has stood for over 140 years on a helical pier foundation (Thomas Point Shoal Lighthouse)

Second, helical piers were never intended to be a "budget" foundation. That's a complete misconception perpetrated by many companies in the industry. The idea that helical piers are a "cheap foundation solution" might sound good for marketing, but it doesn't reflect reality.
Here's the truth about whether or not helical piers are cheaper than other foundation solutions:
Because of their unique and versatile design, helical pier foundations tend to be more affordable than other solutions. They install quickly, don't require as much raw material, demand less equipment, and need less personnel, so they often come in cheaper than other solutions. 
However, a helical foundation could also cost as much as another solution. It really comes down to your specific project and unique needs.
But, if you're thinking about price alone when it comes to your foundation, you're looking at things completely wrong. There's a lot more to choosing the right foundation than simply picking the cheapest one. You certainly can roll the dice and choose the budget option without considering anything else, but is your foundation really where you want to do that?
When choosing a foundation for your project, you have to consider things like:● Foundation performance you need● Soil conditions at your site● Climate forces acting on your foundation● Access to your site - is it remote or hard to reach?● Mobilization costs - how much will it cost to get everything to your site?● Environmental considerations - will you need to remediate the site someday and leave no trace?

Benefits of Helical Pier Foundations

● Faster to install and ready for loading immediately● Requires no excavation or soil disturbance to install● Stable, strong, and secure support in a compact package● Versatile and adaptable to a huge variety of structures and site conditions● High performance in poorly-supportive, saturated, expansive, and other difficult soils● Often more economical to use in remote locations● Easy to install in congested areas near sensitive equipment● Creates no vibrations that could damage delicate infrastructure● Uses standard equipment like skidsteers & excavators to install

Conclusion

If we've learned anything by this point in the blog, it's that there's no cut-and-dry answer to the question:

"How many helical piers will I need for my foundation?"

The reason I can't give you a simple answer is because designing a helical pier foundation isn't a simple process. It takes the combined effort of a team of people, who have to consider a staggering range of factors, to make it all come together. Great foundations don't happen by accident.

When you see how complex helical foundation design can be, it becomes clear why it's so critical to work with a rock-solid helical contractor. Designing and installing high-capacity helical pier foundations for industrial projects is not a job for amateurs or the unprepared.

Thankfully, there's plenty of excellent foundation professionals in the U.S. that put smart engineering first. And while I don't like to brag, our team at S&B Helical takes an engineering-first stance on every foundation we design. 
If you'd like to see if helical piers can help you build better, scroll down to have a chat with a foundation expert.