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  1. #1
    Join Date
    May 2016
    Location
    CA - California
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    1

    Question Home post piers have gaps/empty space around/under them

    Hello,

    First time homeowner here, from SF East Bay, California. Two story ranch-style house built in '69. I've just recently explored my narrow crawlspace and found that many floor posts are in a questionable state. It seems that the soil around posts have shrank and left gaps/empty space around them. Took some pictures below. Is this something that is normal for a house this old, and is it recommended to repair them like by adding screw jacks/etc for proper support? Trying to get a sense of how serious this is. Also, the house foundation itself has a differential of about 2" that did not change in the last 3-4 years. Maybe the settling/foundation change that happened over the years affected the posts as well?

    Regards,
    Ben

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  2. #2
    Join Date
    Jun 2012
    Location
    Escondido, CA
    Posts
    16

    Default Re: Home post piers have gaps/empty space around/under them

    Ben,
    It appears that at some time in the past, someone poured concrete around those pier footings and soil around them is settling/washing away or some other reason. You should hire a structural engineer to make an assessment and advise you on corrective action.


  3. #3
    Join Date
    Feb 2009
    Location
    Southern Vancouver Island
    Posts
    4,567

    Default Re: Home post piers have gaps/empty space around/under them

    Yes, that is not a normal condition, even given the age of the house. Is it possible that the situation has improved, so that flooding is no longer a factor? For example, is there a good storm drain system in this neighborhood?
    I think that looks like damage from flooding, but you are in an earthquake zone there and that may be a factor. No doubt this house has felt a few shakes in its life.

    Did someone perform a home inspection for you?

    Also, we see that your subfloor is plywood on beams on about 4 foot centers, no floor joists. This is an old way of framing a floor, not uncommon where you are, but it does raise some possibilities for sagging floors.

    A layer of poly should be laid down on the bare dirt for a vapor barrier. Concrete can be pumped in under the piers, mud-jacking.
    If the beams are relatively level, the crawlspace could be given a flood coat of concrete for a more permanent floor, but the effort may not be worth it.

    John Kogel, RHI, BC HI Lic #47455
    www.allsafehome.ca

  4. #4
    Join Date
    Mar 2007
    Location
    Santa Rosa, CA
    Posts
    2,500

    Default Re: Home post piers have gaps/empty space around/under them

    Ben,

    Difficult to say for sure from pics, but I am going to be the dissenting voice (so far) here.

    Some contractors would drill piers into the soil for mid-span support and set a pier block into the puddle of concrete left at the top. I believe your area has expansive/clay soil, which is pretty dynamic. If so, the soil will swell when wet and shrink when dry. As a result, soil will pull away from under the concrete during the dry summer months. I am a bit north of you and this is quite common under homes in my area built in the '50s and '60s

    Are you noticing any uneven floors, cracked walls or doors that stick or don't latch? If not, then you might not have a problem. As John already indicated, what did your home inspector say?

    You might notice some flexing in the floors between girders, particularly near large/heavy furniture. In addition, expansive/clay soils can push piers up, which will result in uneven/crowned interior floors.

    Department of Redundancy Department
    http://www.FullCircleInspect.com/

  5. #5
    Join Date
    Mar 2007
    Location
    Ormond Beach, Florida
    Posts
    26,312

    Default Re: Home post piers have gaps/empty space around/under them

    Quote Originally Posted by Gunnar Alquist View Post
    Some contractors would drill piers into the soil for mid-span support and set a pier block into the puddle of concrete left at the top.
    Gunnar,

    Curious as to how deep they typically drilled those hole - are they shallow like a deep footing might be, are deep enough to be 'cast in place pilings'?

    Sounds like cast in place pilings with your description of "and set a pier block into the puddle of concrete left at the top".

    Do you know if the practice was to use unreinforced concrete or would they have steel in the holes when they placed the concrete into the hole?

    Sounds almost like the "puddle of concrete left at the top" was intended to serve as an "unformed" pile cap (no form was use to make a nice square pile cap).

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  6. #6
    Join Date
    Mar 2007
    Location
    Santa Rosa, CA
    Posts
    2,500

    Default Re: Home post piers have gaps/empty space around/under them

    Quote Originally Posted by Jerry Peck View Post
    Curious as to how deep they typically drilled those hole - are they shallow like a deep footing might be, are deep enough to be 'cast in place pilings'?
    Sounds like cast in place pilings with your description of "and set a pier block into the puddle of concrete left at the top".
    Hi Jerry,

    Sorry, I misspoke (miswrote?). These would not have been drilled piers, but basically a regular footing with a precast pier placed on top so the post could be nailed to the wood block. No steel and not remarkably deep. At that time, they pretty much just scraped the topsoil off and went down the minimum 18 inches (or was it 16"? Probably whatever they could get away with).

    Alternatively, if the concrete was stiff enough to pile, they might just place a redwood block with some nails extending out of the underside to "anchor" it to the concrete.

    Quote Originally Posted by Jerry Peck View Post
    Do you know if the practice was to use unreinforced concrete or would they have steel in the holes when they placed the concrete into the hole?
    Sounds almost like the "puddle of concrete left at the top" was intended to serve as an "unformed" pile cap (no form was use to make a nice square pile cap).
    Yes, the puddle was pretty much what you describe. Later, in the '70s and '80s, they would pour the pier footing and then place a paper form at grade level that would make a raised/circular pier when it was filled with concrete. That might get a post base or a wood block as described above.

    Now, most jobs are done with a soils engineer onsite during the drilling as well as a structural engineer on the design team. The holes are drilled down far enough to get into stable soil and the concrete piers are reinforced with rebar cages as well as tied to the grade beams. On the mid-span piers, the section above grade usually uses sonotubes as forms.

    Department of Redundancy Department
    http://www.FullCircleInspect.com/

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