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Community and Q&A

Helical pier and beam foundations VS concrete in cold climate

Luke_O | Posted in General Questions on

Hey everybody, 

I’m in 6A (Minneapolis, MN).  I’ve been researching different foundation types and am curious if anyone in a cold climate has personal experience doing a pier and beam foundation off of helical piers?

I’m trying to wrap my head around why this wouldn’t be a very popular way to build. Is it just that it’s too new? Or am I missing something?

It seems like helical piers VS a shallow frost protected footing/crawlspace/full basement would be a good chunk less money, decrease your carbon footprint, and be a lot faster. The only drawback I can think of is that people where I live are used to, and often really like basements. 

Am I missing something that would make helical pier foundations not nearly as obvious of a winner when it comes to foundations?

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  1. charlie_sullivan | | #1

    I'm personally really excited about it. In addition to reducing the carbon footprint, it can also minimize impact to trees near the site and allow leaving trees closer to the building. Some people advise against trees near your house because of the increase effort keeping gutters clean, etc. but I like the feeling of trees right outside my windows and it's worth it to me.

    As far as why not, aside from the things you mention, the ground temperature is milder both summer and winter than the air temperature, so you need a lot more insulation and probably still have more heat loss through the floor. And the need for structural strength where you connect to the piers leads to thermal bridging. In the end, after working on all that, with details that are unfamiliar to the builders, your cost savings might all go away, but I'd still want to do it, especially if I were building on a wooded lot, or on a lot that would take a lot of site work to build a conventional foundation.

  2. PBP1 | | #2

    I'm in Zone 6 MT, and also I lived in MN (5 yrs). My MT house is mostly (75%) on helical piers (Techno Metal Post "TMP"), as suggested by a high-end architect in Bozeman that often builds on slopes. I have a slab for an attached garage and a small 2.5' deep concrete crawl (10'x10') for sewage/water connections. I built on a small infill lot with 60 yr old Maples and wanted to minimize root damage. I consulted an arborist/forester (UC-Berkeley grad circa 1970, when Aldo Leopold's son was teaching there), he provided a maintenance program (incl. Cambistat treatment) and woodchips for spreading underneath prior to construction (recommendations for root health). Floor lumber is all pressure treated. Two Professional Engineers worked on the load, number and placement of posts (TMP PE was in Colorado). I would recommend finding someone with experience and having at least one structural engineer (PE) involved. Also, prepare water drain layout ahead of time, noting that some recommend installing heat tape along drain lines in a raised floor. Lastly, level, level, level and be ready to shim if needed. Sometimes height issues can arise if welding clamps to the helical posts. As to others unaccustomed to helical piers, some think the "gap" makes the house look "cheap", but that's easily handled if one wants to (deck, landscaping, etc.).

    1. adamcohn | | #4

      How did the raised floor feel on your feet compared with the slab space? Was it noticeably cooler?

      1. PBP1 | | #6

        Not at all, and no floor on slab, just a small 10'x10' section over the 2.5' crawl space, which has a concrete floor, exterior/interior wall foam (of that 2.5' about 1' is above grade) and batts stuffed between the floor joist.

        The raised floor is R-38. We debated on how to construct. I suggested screwing strips to the joist and then dropping in panels between the joist, which would have eaten into the depth of the insulation space. Ultimately, sheets of pressure treated plywood were toe-nail screwed in from above. They had to drill some holes in a few sheets (1") to get a finger in and pull up, those holes were then covered. Overall, it turned out OK. With the plumbing installed, closed cell spray foam was shot from above, followed by batts and then 3/4" OSB, followed by 10.25" wide engineered hardwood 3/4" thick nailed and glued (Bostik Ultra-Set® SingleStep2™ high performance adhesive, moisture control, and sound reduction membrane). The floor is quite comfortable to walk on.

        As to the approach taken, there's an important concern. If you don't protect from rain, the floor will become a bathtub. You need to keep rain out, especially after the spray foam.

        In a 30'x23' great room set at 68F (ASHP) and exterior temperature 17F, the floor is 64-66F with a temperature gradient over about 1' down to 52F at one of the two corners (home perimeter corners). This is due to (i) corners being geometrically a problem for heat transfer, (ii) thermal bridging of the large beams and metal bracket and (iii) perhaps some sealing. I modified the other corner with a 2'x2' piece of R-7.5 foam under the plywood and that corner is at around 55F. I worked at a supercomputer institute where I simulated heat transfer (incl. microwave heating with phase change), corners are always an energy problem (why microwave packages have rounded corners). The brackets at the corners for the helical piers are also larger than others as each supports two beams.

        In sum, the floor is quite comfortable though with a couple areas with gradual height variation (why I recommend level, level, level and experience). In construction, sometimes a few things are not as accurate as planned, though other things turn out fine (even better than planned). My father was a bit of a "Holmes on Homes" character, sent around to fix other peoples mishaps, which helps me to remember, we're all learning ;-)

  3. Expert Member


    Pier foundations are frequently used in very cold climates, especially those where there is permafrost. The complications I can think of off-hand are:

    - You now have to insulate the floor and protect the underside, which is typically a quite large area, and much of that work has to be done from below.
    -- You need to design a way to get services from the floor down to the ground, and from there below the level of freezing. You also need to work out how to run drains through the floor system to wherever this insulated service core is.
    - The area under the house is difficult to landscape and maintain. Over time people often end up adding skirts to conceal the open area, which provides a semi-contained crawlspace, ideal for pests.
    - Unlike a slab on grade, the first floor can't be close to grade, meaning a different relationship to the surrounding landscape, and more difficult access if you ever want to make it handicapped accessible.

    None of these are insurmountable, and a pier foundation may well make sense. They are just things to consider.

    1. PBP1 | | #7

      As to "much of that work has to be done from below", any and all feedback on the "done from above" approach (#6) welcome, I can pass along the info (recognizing that keeping the rain out is a significant concern).

      Also on "close to grade", was a reason why inspector/building dept required plywood, beams and joist to all be pressure treated.

      1. Expert Member
        MALCOLM TAYLOR | | #9


        I'm glad you were able to make it work and not disturb your site more than you wanted to. I have a couple of reservations about the approach generally.

        - In cold climates you are g0ing to want some continuous insulation to reduce thermal bridging at the joists. If you can't work from below that means placing it above, which probably means two layers of subfloor and all the complications that brings.
        - Being so close to grade that you can't access the underside of the floor seem like asking for problems down the road, with no way to inspect or remedy problems in your plywood floor soffit.

        1. PBP1 | | #12

          Thank you, agreed on that continuous layer, and I do have about a foot of clearance, with top soil that is readily movable so I can get access if needed. Again, great points.

  4. Expert Member
    Akos | | #5

    Pier foundation is common enough in cottage country here. Cheap to build, works resonably well but does have the issues people above have raised (extra insulation, critters).

    There is also the issue of resale value. Here the price between a cottage (something on piers) and a house (something on foundations) is enough to pay for the foundation in the first place. As long term value, a proper foundation is a good return on investment.

    1. PBP1 | | #8

      Sounds like a regional/educational issue, as helical piers provide a proper foundation and, in some instances, a superior foundation. In some regions, geology can make piers the preferred solution. And, helical piers can be a solution for a failed "conventional" foundation. Check out the commercial and residential projects (

  5. Luke_O | | #10

    Thanks everyone for the feedback. Good stuff to think about.

    What would you all think of this solution:

    1. Digging out roughly foot or so deep trenches (or more likely the whole footprint) for the treated beams to sit down in on the piers (with some space for them to breathe) That would 1. lower the house a good amount 2. allow for backfill against the rim beam (and I'd waterproof and insulate for extra protection) to prevent critters and help make the house look more normal.

    2. I'd (before backfilling and laying the web floor trusses) get extra long sheets of plywood or ideally zip sheathing (if they sell oversized sheets) and lay them out on top of the beams (if I had to I could temporarily brace the sheathing until I could nail to the floor trusses from below, and after that I would tape the seams). This way I can have an airtight envelope, and with the dug out wiggle room beneath the house Ill be able to attach and tape the sheathing without way too much difficulty. Then I can insulate from above before the sub floor is put on. Obviously there would be a weak spot for the envelope above each pier, but I'd feel just fine about spray foam in a few spots if the rest of the house was airtight

    3. The floor trusses would still be higher off elevation than a normal house but I could find a material to install and bring that to grade (even like a brick or concrete veneer) and then flash above that and side it like normal.

    A few questions/comments:

    Is this a viable option or am I missing some stuff again?

    Do you think the digging defeats the purpose of helical piers or since it would be minimal would it still make cost effective sense?

    There might be water concerns with the dug out footprint, but this is assuming this house has large overhangs and and is graded well and isn't in a super heavy rain area

    I've been a carpenter for just a few years and have no experience being a general contractor for any remodels or new builds so go easy on me haha

    and hopefully all those descriptions made sense...

    1. charlie_sullivan | | #14

      My inclination is to avoid trying to make it look like it's not on piers, but instead find an architect who can use that as an opportunity to make it look more beautiful and inviting than with a conventional foundation. If you want access without going up steps, and the lot is on a slope, there can be a level deck or bridge from ground level on the high side across to the first story of the building.

      1. big__o | | #20

        I agree. hiding the piers makes it look like all mobile homes. IMO. We are on piers and have made the decision to not put up a skirt

    2. Expert Member
      NICK KEENAN | | #17

      I don't get a good feel about a house close to the ground. Check with your local code office, usually 18" is the minimum, I'd want to at least be able to sit up in there.

      I don't think helical piles are a cost saving method, they're mostly used where excavation is impractical.

      I'm working on a house now with helical piles. The top of the pile sticks out of the ground 9" and there is a reinforced concrete wall built just sitting on the ground that encases the pile. It looks just like a normal foundation.

  6. PBP1 | | #11

    Some details:

    Trenches and "allow for backfill against the rim beam". The inspector/building dept were looking for as much clearance from grade as possible. I lived on Humboldt (Uptown) and we had a flood one summer from a heavy rain, over 2' of water in the street (in about 15 minutes).

    Maybe give the experts a call?

  7. Expert Member
    MALCOLM TAYLOR | | #13


    Remember that once you enclose the perimeter of the house to grade, with a foundation wall, rim-beam, or skirt, it becomes both from a building code perspective and practically, a crawlspace with all the attendant requirements including access, ventilation, conditioning, vapour-barriers etc.

    I've built one house, several additions and a few small accessory buildings 0n piers. That means having spent a lot of time on my back with a screw gun trying to add layers to the underside in cramped conditions. Its awful work, usually done by necessity to a lower standard than you would like, and needs appreciably more than 12" clearance to be performed.

    For very small buildings what I have done is build the floor assembly upside down, where I can add rigid insulation and plywood, before flipping the floor. In other discussions here I've floated the idea of making a series of these floor panels that could all be flipped 0nto the beams to form a larger floor - in a way like SIPS. How much sense that makes I don't know.

    Edit: Remember as PBP1 pointed out, most codes require that plywood, beams, and joists that close to grade be pressure-treated.

    1. PBP1 | | #15

      "needs appreciably more than 12" clearance to be performed", indeed, got a 90 degree attachment for my drill to attach the 2'x2' R-7.5 foam at the corner. I'm working on a remote controlled vehicle with machine vision that will carry the foam boards, adhesive and screw gun and install automatically (I wish!).

      1. Expert Member
        NICK KEENAN | | #16

        My idea is a trained monkey to get into those tight spots.

      2. Expert Member
        MALCOLM TAYLOR | | #18

        You build it, I'll buy it!

  8. GBA Editor
    Kiley Jacques | | #19

    Hi Luke,

    I have scheduled a post for this Friday that you will want to read called "All About Helical Piles." Scott Gibson spoke with a number of builders who have used the system in different applications. Come back and check it out.

    1. big__o | | #21

      I cant wait to read this. Ours is done, now we need to tackle insulating it. Code minimum is r19 in zone 3a

    2. Luke_O | | #22

      Sounds great, I'm looking forward to it!

  9. MaxQ | | #23

    HI Luke,
    I am in Zone 3 so I have a much more temperate climate, but I am in the process of building on expansive soils. The soils report I got details pier and grade beam, at 8 feet minimum depth with a 12 inch diameter. The Helical piles run 150 to 350 and up depends on the pile size and depth. In my situation I probably be in the 250 range so looking at the speed of the pile installation and how it fits with what I am doing it makes sense, but I haven't gotten to a must decision point yet.
    I plan on keeping the piles buried because above grade piles are band by some cities ( I am in California and before the comments start... yes the land of fruits and nuts that billion dollar industry). I have designed my grade beam using concrete and insulated concrete forms. The ICF makes things insulated and sort of traditional and allows for a bit of float for the wall position. I also need voids under the beam so the Lego like forms that stay in place after the pour are a nice touch.
    The draw back for the piles either for wood beams or concrete is the positioning the piles. (not that accurate rocks can be a pain)
    The process of drilling the piles means there is some variation to the pile accuracy for building layout. Check out the techno metal post web site for Alaska they are doing what your talking about, they also have costs.
    Good luck, if you interested in the design you can P.M. me.
    I will add a graphic I did in Sketchup to this post its very crude so be nice.

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