The Processes of Building A Datacenter
The demand for datacenters is on the rise. If you’re a mid-to-large enterprise and don’t already have your own datacenter, [...]
Piers and footings are among the most important parts of a building’s foundation.
Drilled deep into the ground below the foundation, piers support the weight of the building for decades, withstanding normal use and often destructive foundation settlement.
Two of the most popular materials for piers are concrete and steel.
But how do they compare?
Is one better than the other?
Keep reading for our comparison of concrete and steel piers. We’ll help you decide once and for all which is best for your commercial building.
Table of Contents
1. Installation (Time and Process)
2. Alternative Installation Methods
3. Durability
4. Longevity
5. Depth
6. Building Size and Type
7. Pricing
As a business owner, it’s only natural to keep a finger on the pulse of your company’s commercial construction projects.
Whether it’s pouring a foundation, tilting up concrete walls, or drilling piers into a freshly graded lot, you’ll probably have the same two questions:
We’ll explain each process below (and we’ll try not to use too many confusing construction terms).
The terms “piers” and “pilings” are often used interchangeably when discussing underground concrete foundation supports.
In this section, we’re strictly referring to piers.
In the drilled concrete method, the crew uses an auger — a type of heavy machinery that resembles a massive corkscrew — to drill a vertical hole called a “footing” beneath the foundation.
The exact depth of this shaft depends on a few factors, but none is more important than the local climate. A general rule of thumb is to drill at least one foot beyond the “frost line,” the depth where soil no longer freezes in winter.
This number can vary from 100 inches in notoriously cold states like Alaska to just four inches in Louisiana and South Carolina.
The drill rig operator removes soil and rocks from the drilled caisson in small increments until the hole reaches the ideal depth (usually 12–15 feet) and diameter (12–66 inches).
The drill rig then inserts steel rebar into the hole to boost the pier’s tensile strength. Next, the crew pours concrete into the shaft and allows it to cure to near-full strength, which could take as little as a week.
Shortly after pouring the concrete and installing the rebar, the crew may fill the gaps around the pier with “backfill,” like the previously removed soil or several inches of gravel.
This step reinforces the freshly poured pier to prevent future shifting. Some piers also feature a steel post base positioned in the center.
The steel pier installation process is generally much quicker and less labor-intensive. It all begins with digging small holes, either by hand (for smaller shops and buildings) or with a smaller variation of an auger drill.
If this is a foundation problem repair, the crew will install temporary brackets along the foundation. Next, a hydraulic press is used to drive steel pipe segments vertically into the ground.
This process continues until the first steel pipe becomes lodged into a firmer sub-strata beneath the earth’s surface.
The crew then either shifts the weight of the structure to the newly laid piers or allows the slab foundation to rest on the piers in the current location before backfilling the gaps surrounding the tubes.
Steel piers cut this process down to a few days for larger commercial structures. The concrete alternative can take several weeks.
In addition to the more traditional pier installation methods, each version has an alternative that may fare better in different construction projects.
What are the different types of pier foundations within each category?
The most common alternative to traditional drilled piers is called “pressed pilings.” What makes this method different are the steps that follow the hole-digging process.
Rather than pouring freshly mixed concrete directly into the hole, the work crew presses 12-inch tall precast concrete cylinders into the hole.
A hydraulic tool then forces each segment into the hole until it reaches the point of refusal — or where it can’t go any further. Compared to the drilled concrete approach, pilings require less time to install and fewer masons.
For buildings that have grade beams and need foundation repair, this route is a safer option. The crew will dig holes directly beneath the grade beam, position a pile cap on top of the piles, then straighten out the slab.
The construction industry modernizes itself with each passing year. With that, helical piers are quickly becoming the future of steel piers and pilings.
Unlike classic steel piers, which involve segmented pipes hydraulically pressed together, the helical version looks like a large, helix-shaped screw.
A high-torque machine will twist these piers into the ground, lodging the blades into the soil for a secure fit. The on-site crew then adds steel segments to the top of the pier until they reach load-bearing soil.
This steel pier alternative is generally best for lighter structures built on weak or unstable soil.
Next up is the durability factor. Once a construction crew forces those piers deep into the soil, how well will they handle the elements and the weight of the foundation and building above?
We “rate” the compressive strength of concrete in the form of PSI — or “pounds per square inch.”
In layman’s terms, concrete with 3,000 PSI could carry the load of an American Bison in a single square inch of surface area.
Concrete piers typically support 3,000–4,000 PSI.
This load-bearing capacity can easily redistribute the weight of a small-scale structure across its piers without cracking its foundation.
But to further strengthen the concrete, contractors recommend reinforcing bars (rebar). These steel rods add tensile strength to the concrete to prevent cracking and excess shifting when the ground settles.
However, it’s not an exact science, and concrete piers do sometimes fail.
Steel ranks high on the list of the strongest metals on earth, making it an obvious choice for stabilizing heavy or multi-story buildings on loose soil.
Steel piers are considerably stronger than concrete, with a 55,000–60,000 PSI rating. This is equivalent to the weight of 20 giraffes stacked on a single square inch of steel.
Steel piers are essentially solid metal pipes forced deep through the earth to lift a building’s sinking foundation back into place. The durable steel tube resists cracking and chipping in all directions for a permanent solution.
But that doesn’t answer the question in the back of your mind:
What happens when it inevitably rains or snows?
Left untreated, the acidity in rain and minerals in the soil corrode steel piers and wear away at their structural integrity. Yet, steel that’s galvanized adds a protective molten zinc coating to the metal that resists corrosion.
Galvanized steel piers are great for large buildings with deep soil and wetter areas like the Pacific Northwest.
Another major concern when contracting out a multi-million dollar build is longevity.
How long can you expect these foundational beams to last before they need replacing or repairs?
Or will they last forever?
The 1–4-week gap between the concrete pouring and curing phases seems like a lifetime.
That fact is true whether you’re installing them before construction or decades down the road to correct a sinking foundation.
Generally, concrete piers can last 75+ years without issue.
Of course, outside factors may cut their lifespan short. Here are some of those factors:
For the sake and safety of the entire structure, it’s better to hire a more skilled subcontractor using high-quality concrete and reliable methods than saving money on a crew that cuts corners.
Steel piers are a relatively new invention compared to traditional concrete piers. But as technology advances, their life expectancy is also widening. Many steel piers installed 50–75 years ago are still functioning optimally.
Meanwhile, non-galvanized steel piers may require replacement or repairs sooner due to corrosion in areas with mineral-rich soils and heavy rain.
By “depth,” we mean how deep an excavation crew can drill or press these piers into the soil beneath the foundation.
Remember: Piers stabilize foundations poured on unstable or settling soils.
The added structural integrity comes from the steel or concrete piers being pressed deep enough into the soil to hit a load-bearing rock. Of course, the depth of that layer depends on your geographical area!
But how deep can we drill or press concrete and steel piers?
Drilled concrete piers can typically penetrate 10–15-feet of soil. Unfortunately, this depth won’t support a large commercial building like a factory or a distribution center built on deep soil for long.
However, it’s popular for lighter structures (like pole barns or riding arenas) erected on shallow soil. This method may not reach a solid layer of earth that can support the concrete piers plus the building.
The more advanced hydraulic piling method rams concrete piers into the soil with three times the force of the structure above it — up to 40 feet deep.
Similar to concrete pressed pilings, the steel pier route rams pipes into the soil with a hydraulic pump until it detects a solid sublayer.
This device can lodge steel piers up 75-feet deep, ideal for larger-scale commercial buildings sitting atop deep soil. They’re also durable enough to support ten times more weight than traditional concrete piers.
It’s safe to say that what works in the residential construction industry doesn’t always work in the commercial world, and vice versa. The length, width, weight, and height of a building all determine which type of pier is best.
While they don’t live up to the tensile strength of steel piers, concrete piers can replace steel piers in most instances without a noticeable difference.
However, they’re far better choices for smaller structures that weigh less, including sheds, shops, or small storage facilities.
Steel piers’ durability, depth, and longevity make them the best choice for larger buildings. That includes multi-story office buildings, skyscrapers, data centers, storage facilities, and apartment buildings.
Our last — but likely most important — comparison is the price factor.
How much should your company expect to spend on piers or footings to reinforce your building’s foundation?
The final price tag depends on the size of the concrete slab, how far apart the footings are spaced, and how many piers it needs for adequate support.
Concrete piers cost between $500 and $1,000 per pier and require less manual labor when hydraulically pressed into the soil rather than drilled.
Based on upfront costs for materials and labor, concrete piers are the more budget-friendly option for businesses with limited funding and small shops.
High-grade steel piers cost around twice as much as concrete piers, averaging $700 to $1,600 per pier.
Steel is almost always worth the extra cost for commercial buildings considered long-term investments.
In fact, in many cases, it’s the only option.
Steel is the most logical long-term fix for buildings sitting on 70+ feet of unstable soil or for taller, heavier structures (i.e., warehouses or skyscrapers).
Between the two popular pier options, steel is tougher on the company’s construction budget than concrete.
But, it has several benefits:
Piers are also a much more complex concept once we zoom away from the commercial edge of construction.
For example, you can DIY piers for decks and sheds or raise a home’s foundation by 12+ inches with a concrete pier foundation.
Ultimately, it depends on your situation and needs. If you are planning a commercial construction project in the Colorado area and want insight on the best pier option for you, feel free to reach out to us at 303-337-6982 or admin@fmpconstruction.com.
