You bit the bullet.
You got fed up with the grotesque cracks crumbling down your drywall, the stupid, uneven floorboards that make you feel like a tipsy seadog about to sing sea shanties, and the stubborn sticky doors that have you pumping iron like you’re getting ready to fight Rocky.
You flipped through the phonebook – found an exorcist (changed your mind), then found a foundation specialist.
The inspector shows up, runs through his encyclopedic checklist, completes a floor elevation survey, and writes up a proposal he wants you to sign in blood.
Helical piers. He tells you, you’re gonna need a helluva lot of helical piers.
The words taste foreign on your tongue. The term invokes a shape you haven’t needed since 8th-grade Geometry and ships and oceans.
So, being the digital native internet savant you are, you Google: what are helical piers?
We here at Dalinghaus have covered this topic exhaustively in other articles, but did you know there are different types and sizes of helicals?
In this article, we are going to address the two kinds of helical piers (think binary code – 0 or 1)
The two types of helical piers are:
Round Shaft Square Shaft
The dos tipos of helical piers are installed in a similar fashion – via a hydraulic drive head.
Both types are available in various shapes, sizes, and lead helical configuration.
In this article, we will go through some of the applications in which helicals are utilized and explore which types of helical pier perform better under what circumstances.
Helical piers are not a one size fits all – you can’t fit a round peg in a square hole so to speak.
The Differences Between Round & Square Helical Piers
The primary difference, as indicated in the name, is the shape of the helical piers.
Round Shaft helicals are constructed out of spherical pipe/tubing (think pi, think circumference, think doughnuts).
Square shaft helicals are made up of a solid steel square shaft (think boxing-ring, think Rubix Cube, think chicken and waffles).
Round Shaft Helicals are excellent for vertical or compression loading. In laymen’s terms – they support structures and/or loads that move up and down.
Square Shaft Helicals work best for lateral or horizontal loading. In laymen’s terms – they are perfect for any structure and/or loads that move side to side.
Shaft sizes are another difference between round and square helicals.
Square shafts have a max size of 2.5”.
Round shafts can be as large as 48” in diameter.
Of course, the diameter and size of the shaft implemented are dependent upon the individual load requirement.
The Type of Load: Why it Matters
As previously outlined, round shaft helicals are implemented for vertical and/or compression loading.
If you like Europop-electronic-dance-slide vibes, just remember the Vengaboys’ smash hit Up and Down.
Round shaft helicals are used to stop your funky foundation from bobbing “up…and down.”
Square shaft helicals are utilized for horizontal/lateral loading. They impede side-to-side movement like the kind typically found on dead disco dance floors. (*Note – Dads, a helpful hint, bellbottoms are out).
Now, these aren’t arbitrary distinctions between the uses of square and round helicals. There was no foundation-construction-guru-Godfather-Family meeting where it was decided what is what.
This is science. There are equations, proofs, and theorems that take up entire university blackboards that explain why round helicals work better here and square helicals work better here.
Trust us, we would love if they worked the same – then we’d only have to keep 1 kind in stock!
One would think that square shafts would work better in general.
I mean, come on, it’s a rock-solid steel bar and the round shaft is just a hollow piece of pipe. The truth is, square shafts bend when utilized in a retrofit or foundation repair application.
An eccentric (or lopsided) load can put strange pressure on the bracket (imagine waking up with a crick in your neck. Same principal of pressure).
The solid square shaft tends to bend out from the bottom of the T-Pipe of the bracket and the helical shaft. At this point, not only will the shaft bow, but it is more susceptible to arcing in the deeper soil below.
The number one rule in the foundation game is: bent pipe is useless.
Round shaft helicals take this pressure much better when loaded with a vertical load. The spherical shaft of the helical absorbs the eccentric loading far better than any square shaft.
Being able to absorb the eccentric loads of a retrofit bracket is the primary reason round shafts are preferred in foundation repair applications.
Tension Loading – two pulling or opposing sources that stretch an object trying to pull it apart. In other words, imagine that our tiebacks are playing a constant game of tug of war with the earth.
Square shafts are ideal for tension loading due to their smaller surface area (when compared to a round shaft). Most of the tiebacks utilized on a residential home are only 1.5” versus the larger 3” shaft on the round helidal.
The size of the helicals (the actual screw section) will remain consistent on both shafts. These massive threads screw into the earth and lock into place in competent soil.
Because square shafts don’t have any additional “skin friction” (compared to round shafts), they are able to be installed into deeper into soils.
Square shafts are not as impacted by soils building up loads at a more shallow depth – thus, they lock into more dense soils that ensure their capacities.
When tension loads are installed to the shafts, the solid bar of the square shaft holds up significantly better than the hollow spherical bar.
This is due to the fact that the holes for the adaptors and extensions have a thicker area that won’t allow for the bolthole to sheer/elongate.
The round shaft helical’s hole locations are only being held by about ¼” steel, where the square shaft has a solid 1.5” of steel that needs to give way to tension loads being applied.
How do we know which type to use?
Experience. I’ve been in the foundation repair business for 15 plus years. In the old days, we were told to utilize square shaft helicals for every job. This was the industry standard.
Due to advances in technology and information, the industry standard has evolved to embrace the 2 different types of helicals.
Since we’ve transitioned, we have experienced better results and happier customer satisfaction.
What’s the Next Step?
If you are in the beginning stages of your foundation repair-life-cycle and still conducting your own research, then you will most likely soon be ready for a foundation inspection.
Foundation inspections are FREE with most construction companies (unless you are in the middle of a real estate transaction).
You can book your Free Foundation Inspection through the button below.