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  • Pier foundation durability

    The JLC article about pier and beam foundations reminded me of a question that puzzled me before.
    You notice that these piers have uncoated, rusty rebar. And the pier itself is not waterproofed in any way. So you have a piece of concrete sitting in wet soil, probably saturated semi-permanently. The rebar is going to rust at a pretty good clip and eventually be of zero structural value. It may be 50 years or 100 years, but it's guaranteed to happen. Not only that, but rebar as it rusts increases its volume so is likely to crack the concrete. I've seen it happen in garage floors.
    How do these folks monitor the structural soundness of the piers and decide when it's time to tear the whole house down and start all over?
    Allan?

  • #2
    One thing is that concrete is extremely alkaline so that unless there is a crack that is allowing direct water and air penetration the rebar is pretty well protected from corrosion.

    Introduction of chlorides (salts) can reduce the alkalinity and speed corrosion.

    And, yes, everything will fail eventually, but if you use good quality concrete with good coverage, corrosion of the steel shouldn't cause premature failure.

    kevin
    “It is difficult to get a man to understand something, when his salary depends on his not understanding it.” - Upton Sinclair

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    • #3
      Originally posted by kfc510 View Post
      ... shouldn't cause premature failure...
      kevin
      I understand that, but fail it will, prematurely or post-maturely. Let's say 150 years. We have perfectly serviceable houses that were built over 100 years ago, so it's not unreasonable to expect that we'll have houses built today that are perfectly serviceable 150 years from now.
      I'm confident that when the rebar is gone the piers will collapse. I'm just wondering how you inspect or monitor for it other than waiting for a catastrophic failure.

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      • #4
        I have not fully read the article yet but do seem to recall that it is a technique used more in the Texas area, maybe other areas that are known to be drier climates. So maybe rusting rebar is not as big an issue as some of would think.

        I find it interesting the use of cardboard forms and the mention of termites. Seems like an open invitation for termites to me.

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        • #5
          I have not read the article yet either but epoxy coated rebar is the way to go.
          Portland Renovations, Inc.
          www.portlandrenovations.com

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          • #6
            Right. When you build a regular house on a basement, there is waterproofing on the outside, drying to the inside and drain tile at the bottom, so the concrete walls and footings are kept relatively dry.
            We don't build on piers around here, but what caught my attention was the discussion of how clay is unstable and how it moves around when soaked. With enough force to crack concrete. And how that's a large reason why they build on piers. So I'm assuming the piers will be soaked regularly if not permanently. Yet the pictures show bare and rusty rebar.
            Just wondering...

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            • #7
              By that time Trumps wall will be done so well have plenty of cheap labor to swap the piles out.
              "First we finish the game, then we’ll deal with the Armada!"

              Sir Frances Drake

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              • #8
                All of our foundations have been pier and grade beam since 1975, even now with the simpler IRC it defaults to Chapter 17 of the IBC if there are piers (also welds, and epoxy) requiring Special Inspection. All Special Inspectors require all rust on rebar (or bolts) be sandblasted off prior to sign off.

                That being said in 1958 a guy right on Grove Street in Berkeley had me tear out a collapsing garage built in 1905 and replace it with a carport, when I tore down the old cracked concrete walls I found that there was no rebar left, where it had been were rusty tube holes, but amazingly the old carpenters had failed to knock out their wood spreaders, the wood spreaders were still in tact and the wood was as good as the day they were left in in 1905. We do have termites in this area, I have no idea why termites never got to the spreaders. I'd say the reason the steel rusted out in 53 years was the original mix was terrible, I could see all kinds of honeycombing and even clods of dirt in the walls, I guess everything was mixed by hand in those days and sometimes a shovel would pick up some dirt when picking up aggregate.

                In 1969 I visited Brasilia to see the beautiful modern architecture, one of the things I noticed was poor quality concrete with chunks that had fallen out, I don't think they had ever seen a vibrator, looking at buildings under construction even high rises they were mixing concrete on the ground in cement mixers pushing it up multi-story switchback ramps in big 4 wheel wheelbarrows.

                Ted, I understand that Trump's wall is going to be beautiful, I also understand that you have been up in Vermont skiing with Martin and Riversong, how do I know? A guy up there sent me a picture of you skiing up there
                Last edited by Dick Seibert; 03-19-2017, 11:59 PM.
                “President Obama doing well. His approval rating is at 51%.--- The other 49% are taxpayers.” Jay Leno

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                • #9
                  One thing is for sure, the builder in that article, Matt Risinger, ALWAYS goes above and beyond and strives for perfection. I'll forward this to him and see if he'll weigh in.

                  I can understand your concerns though. We don't build with pier and beam. I understand the concept but, have never built that way.

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