Foundation Repair-Underpinning with Hybrid Piers

The three most common ways of underpinning a home foundation in need of repair are steel piers, pre-cast concrete cylinders (or push piers) and the drilled bell bottom piers. Each method has it’s pros and cons and affects the cost of foundation repair.

Steel piers can be shoved into the ground deeper than concrete cylinders because they have a smaller diameter. Using concrete cylinders provides more surface area for the “skin friction” concept of engineering. The drilled bell bottom piers is the oldest method of foundation repair and still widely used although this method takes the most time.

I’m watching TV the other day and here comes a commercial for the Olshan foundation company pitching a combination of steel and concrete cylinders for a foundation fix.

Here’s the claim:

  • The steel segments provide added depth. The concrete sections offer greater bearing area which provides better support.
  • The larger diameter concrete cylinder provides more surface area for better support. The smaller diameter steel segments penetrate deeper into soils not affected by weather.
  • Cable Lock™ ST penetrates deeper into tough soil conditions. Once a foundation repair piling is driven past the weather affected zone, it provides better support.
  • The combination of concrete and steel adds up to a repair that is deeper and stronger.

So basically steel piers are pushed into the ground first right at the edge of your concrete slab foundation. Then a transition segment is added to go between the steel and concrete cylinders. The cylinders are stacked upon each other until they almost reach the foundation, creating a piling. A pile cap is added to the top of the stack where two sets of spacers can be used to transfer the load of the foundation to the new piers.  It’s kind of hard to describe, but you can see a diagram of it on the Olshan website.

If you choose the ST Plus system, a steel cable is strung through the entire pier. The cable is used to confirm the depth of the steel segments and align the concrete cylinders.

The structural engineer I hired to inspect my foundation is not a big fan of the concrete cylinder method of foundation repair. Why? He said there is no way of knowing for sure that one or more of the cylinders in the stack hasn’t broken, or is misaligned. No way to inspect for that possibility. He said 90 per cent of the time, it works OK, but he prefers to be sure. So I’m thinking the steel cable through the stack is a way of attacking that problem.

So is this really a better method of foundation support or a marketing gimmick? I’d love to hear from some foundation repair professionals about this hybrid underpinning method. Please leave a comment below. Thanks.

Tags: , , , ,
Previous Post

Water Foundation – What’s Up With That?

Next Post

House Foundation May Need Some Underpinning

Comments

    • Bob
    • May 13, 2011

    Hey Digger,
    Not a bad site for someone not in the industry. I have a couple of comments about the Cable lock vs Steel piers.

    First, I’m in Arizona, where the soils are hard. you would never get a large concrete cylinder in the ground, so it may be rather moot for here.

    Second, I am not sure the cable helps with concrete cylinders that could crush durning installation. the cable would only help keeping the system together in tension and provide little help in compresion.

    Although the cylinders have greater friction as you mentioned, the goal may not be more skin friction. Sometimes more skin friction results in more risk of downward drag, a term used whent the soil surrounding a pile grabs it and pulls it down. The better strategy might be to rely on end bearing, something smaller diameter steel piles could provide more efficiently.

    Concrete cylinders may present a more favorable cost solution and in some cases do the job just fine.

  1. Hi Bob,
    My father-in-law lives in Green Valley just south of Tucson. So yeah, I can’t imagine trying to push a concrete cylinder into that ground.
    Thanks for the comments,
    Digger

    • Frustrated
    • September 23, 2011

    Just bought home less than 2 yrs ago w/lifetime warranty w/Olshan. They sour not return calls. When wanted to c/o to their boss in Knoxville, secretary said she didn’t know his name or number. The finally gave me manager’s Todd Ruxer cell number, but it was fax number. Needless to said their concrete system failed. Only installed ’08. They finally called back after c/o w/ BBB and said we cut down a tree in front, so their work in back is no longer covered. They are a sham in Tenn! B-dry is fixing w/steel piers for total 12,000. Do not buy hius w/Olshan warranty

    • Yvon
    • January 20, 2015

    That is interesting, I recently started working in construction, but I have never done any underpinning. I understand the concept, but I wonder what the method is of actually doing it. It is amazing that we do have a way though of inserting metal pins underneath one’s foundation.

    Yvon Lebras | http://harmancontracting.com.au/underpinning/

Comments are closed.