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Product Guide
All About Helical Piles

A thriving industry offers concrete-free alternatives for additions, deck footings, and foundation repair

No freeze worries here. Carpenters can begin building on helical piles as soon as they are set, with no concerns about placing and protecting concrete in the winter. These piles will support an addition. Photo courtesy Scott Gibson.

Plans for the 400-sq.-ft. addition looked straightforward: a new dining room, a pantry and a full bath stretched out along an existing wall of the house. Ordinarily, the wood-frame structure might have gotten concrete footings and stem walls if not a full foundation, but designer Michael Maines decided to build the structure on helical piles instead.

“She doesn’t care about additional basement space; she wants to keep costs as low as practical; and she doesn’t want to create unnecessary carbon emissions or other negative environmental impacts,” Maines said in an email about the project for his mother-in-law. “Additionally, access is tight and the septic system drain runs under the addition . . . So piers just seemed to make sense.”

The 10 hydraulically driven steel piles will cost the homeowner $3,000. Maines, a builder and designer as well as a contributing editor at Fine Homebuilding magazine and GBA Expert Member, didn’t price out the concrete work, but he guesses it would have cost twice as much as the piles. Then there was the excavation and related issues he’s also avoiding.

Maines’s decision to opt out of concrete in favor of helical piles neatly sums up their appeal on both economic and environmental grounds: They are faster, less disruptive to the building site, and often cheaper—and with none of the carbon baggage that comes with concrete.

Those advantages are helping to propel the industry into a new era, 182 years after the first helical piles (then called screw piles) were used to support a lighthouse on the coast of England. While builders like Maines may choose them for new construction, they are more often used in residential work for foundation repairs and reinforcement. On commercial and industrial projects, helical anchors and helical piles have a variety of uses.

Despite their…

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  1. Max E | | #1

    hi, thanks for posting. i dont quite understand this statement
    "When piles are not cut off at or near grade, a structure built on top of them may have a tendency to wobble. The problem can be corrected with bracing that’s welded to piles, or by leaving the tops of the piles closer to ground level."

  2. User avater Expert Member
    Michael Maines | | #2

    Max, because helical piles have a small diameter, they don't have very much resistance against lateral movement. If you're placing girders directly on them it may not be an issue, though I know of a project nearby with that situation and when you walk on the floor system it shakes a bit more than it would on a regular foundation. When the floor system is built up on posts, as mine is in the project Scott photographed, there needs to be angle bracing to keep the posts from shifting. On my project we'll add diagonal 2x4s, but if you wanted to you could extend the metal piles higher and weld or clamp a metal brace instead.

    1. Charlie Sullivan | | #3

      I was wondering, looking at the picture, how that was addressed. Did designing that added bracing require getting an engineer involved?

      That space looks a whole lot more pleasant to work in than a crawlspace.

      1. User avater Expert Member
        Michael Maines | | #4

        Charlie, the project is in process--we just stood exterior walls yesterday. It's attached to an existing house so lateral resistance is not as important. But after we drop 2x4 sub-joists below the 2x10 joists to get a 13" insulation cavity, and cover that with plywood for air and critter resistance, we'll add diagonal 2x4 knee braces at each post. It's definitely a more pleasant space to work than a sealed crawlspace, aside from the fact that we put down 3/4" crushed stone and I keep forgetting my knee pads. We'll eventually wrap the space with vertical board skirting.

        If I was designing a new house to be entirely on piers, I would get a professional engineer involved. Techno Metal Post also has engineers on staff who can answer a lot of questions.

        1. Expert Member
          Malcolm Taylor | | #5

          To me the two photographs illustrate how many of the weaknesses of the system can be designed out. The floor of the outbuilding supported directly on the piles would be difficult to work on, leaves an awkward space underneath, and the exposed piles, although structurally adequate, look unfinished, flimsy, and temporary.

          That airy underside of Micheal Maine's addition avoids all those issues. If the floor, and attachment 0f the walls to the existing house, provide adequate shear-resistance, I'd be inclined to try and not add bracing to the posts.

          1. User avater Expert Member
            Michael Maines | | #6

            Malcolm, my situation was just lucky in that the existing first floor was already high above grade, but at minimum I use the IRC minimum clearance of 18" between grade and the underside of the floor system. I've crawled through 10-12" spaces and it's not fun at all. (Beams can extend below the 18" clearance.) But even 18" can leave the floor system higher than a conventional foundation.

  3. Chris Hovious | | #7

    Hi Mike,

    Do you have any information on the plumbing chase below the structure?
    I'm working on a design on helical piles and have a few hairbrained ideas, but curious what you've come up with.


    Edit: I just re-read and realized I was confused. Sounds like there was existing plumbing under the addition, not new.

    1. User avater Expert Member
      Michael Maines | | #8

      Chris, we are adding a bathroom so there will be plumbing in the floor assembly. I was careful to lay out the joists so the toilet drain can go straight back to the house, and the shower and sink drains can be drilled through the 2x10 joists to tie in with the toilet drain. The 2x10s are larger than structurally necessary, partly to allow for drilling.

      Yesterday we gusseted 2x4s to the bottom of the 2x10s so we have about 13" in the floor cavity. More than half of the insulation will be below the drain so I'm not worried about freezing. My insulator does a lot of floors on piers for seasonal lake homes, and he likes to make a removable polyiso foam panel below plumbing chases. We may do that here but I'm not sure yet.

      On a previous project we used oversized I-joists for the floor system, which allows you to drill holes for plumbing, reduces thermal bridging and allows longer spans.

      Another idea I designed for a current project before the builder decided to go with a slab system for time and budget reasons (WarmForm by Bygghouse) was to make a small crawl space, about 10' x 10', and put the rest of the structure on piers. That would have given us a place to make plumbing connections and also would have braced the entire floor system against lateral movement.

      What are your ideas?

      1. Chris Hovious | | #9

        Hi Mike,

        Thanks for responding! I'm planning a build on piers, which I'll hopefully start next summer.
        I'm thinking web joists for the first floor & pack with dense-packed cellulose. If they're deep enough, I don't think I'll have to worry too much about the lines in the floor.
        What I'm stuck on is how to get the well & septic lines into the house, and how deep to go with that detail.
        I thought of just many layers of foam board with some sort of wood-walled "basement". Maybe a 4'x4' or something smaller.
        I've also considered a small concrete chase, then insulating. This would help with lateral strength of the house (something I'm still not sure how to accomplish well on a building entirely on piers).

        My goal is no concrete. I may have to grin-and-bear a slab for the garage. I'm not sure if I can afford all the lumber & time it'd take to make a strong enough floor to park on. TBD.

        I once built an addition with a kitchen on piers. The inspector gave me the idea to box-in the plumbing in the stud bays and *not* insulate in front of them. I used the thickest foam board I could fit behind/above/below and made a small insulated cavity to the drywall. Then I caulked/sealed it all the way around. The end result was a highly air-sealed, reasonably-well insulated cavity, covered by drywall, that could stay "warm" by the conditioned space.
        I built that addition for a friend many years ago in Burlington, VT. I'm fairly certain it hasn't had any issues, yet.

        1. Expert Member
          Malcolm Taylor | | #10


          I've done a couple of insulated cores. After working out the kinks (the first was too small relative to the height from floor to grade and kept freezing), on the last I poured a 4 ft x 4 ft square of concrete stem walls. with foam interior insulation continued down to the frost level. I located it under a utility room, and left most of the top open so that it relied on the heat of the house, rather than supplemental heat. That meant that if it froze, the rest of the house had too, and you had bigger problems to deal with. Once done it is vitally maintenance free and can be forgotten about.

          1. Chris Hovious | | #11

            Thanks Malcolm! I'm in Maine, Zone 6a (wet). Frost is 5-6ft. I was thinking something similar to that. You found that 4x4 worked well, it sounds? What size was too small?

            Edit: I read some of your other comments on this matter. Good advice! Thanks Malcolm!

          2. Expert Member
            Malcolm Taylor | | #12


            My advice is all based on my experience here on the milder West Coast where the frost level is around a foot. There may be more efficient ways to deal with protecting the core when it has to go as deep as you would have to. Perhaps using wing insulation as they do with Frost Protected Shallow Foundations? I hope Michael or some others will chime in with their thoughts on that aspect of the design.

        2. User avater Expert Member
          Michael Maines | | #13

          Chris, on a new home on piers in Harpswell that I was involved with we used thick sheets of EPS foam to make a transition box for utilities--kind of like a mini-basement. Pretty much like Malcolm describes except without the concrete. I think the carpenters ended up wrapping the foam with pressure treated plywood, which would help with UV and critter resistance.

          1. Chris Hovious | | #14

            Thanks Mike! That's kind of what I'm hoping to do. When I do basement/dug-out egress windows I usually box it in with 6x6's. I was thinking the same thing, just lined with several layers of EPS.

            Pic: /wp-content/uploads/2020/09/egress-window-basement.jpg

          2. Darren Adams | | #15

            Michael, All: Very happy to read this article. For an upcoming Passive build, referencing Mr. Maine's excellent article on minimizing concrete in a slab on grade foundation vs optionally a foam-encapsulated raft slab foundation a la Warmeform. In a variant of your stem wall or perhaps an improvement to a thickened edge raft slab, I've been pondering for a while using helical piles to improve both anchoring and support while reducing total cement required. General idea was scrape topsoil, insert helicals and then tie their post caps to the ring and intermediate support beam's rebar before pouring with presumptively minimized concrete. Same idea for the EPS-encapsulated raft slab: screw in the piles before dropping the foam on top of them, then proceed as normal. Solves the problem of cross-bracing. Not sure this makes sense when I see the linked installed costs survey results. However, would welcome thoughts or comments. Thanks in advance.

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