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  1. #1
    Join Date
    Sep 2012
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    Eastern Kansas
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    104

    Default Pouring New Piers Around Existing Ones

    The bigger picture is here -- https://advice.thisoldhouse.com/showthread.php?t=121829 -- but one part of this is pouring new concrete piers to support a covered porch/deck.

    Is it OK to dig around an existing pier -- and pour concrete around it to make the existing pier larger? Could I just dig with a clamshell digger and enlarge as I need? Do I need to clear out all around the existing 6" peir and sit a new 12" tube around that existing pier? Do I need to completely remove the existing pier? They are probably 24 to 36" deep.

  2. #2
    Join Date
    Dec 2007
    Location
    Tennessee
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    1,381

    Default Re: Pouring New Piers Around Existing Ones

    You have read all my existing posts so I will not repeat them. Heres what I would do in your situation. I would dig out the footings (this is the correct term for the part of the underground support) at the corners only. Leave the rest in place, untouched. Then hire someone with a tractor and a 12" to 14" diameter post hole digger and put in new holes, 36" deep at the corners and equally spaced down the line between the corners, but at different locations than the existing footings. Maybe add one extra footing so they are all spaced a little closer together.

    If you have a truck or SUV or even a car with a good towing capacity, you can go to a concrete facility and get one of those tow containers that hold about a yard of concrete and tow it to the house to fill the holes to make the new footings. Be sure you have all the rebar in place before doing this. I would not use any tubes or forms, just pout into the hole up to ground level. Each footing should take about 3.2 cubic feet (14" diameter) of concrete. If you are doing more than 20 footings, you may just need to have a truck deliver it for you. If you are flexible on your schedule, you may be able to get it tagged off of another job and save some money.

    You could also rent/buy a concrete mixer and DIY, but don't do it by hand with a hoe and tray, that is way too much work.

    Now build your piers out of concrete block and the rest of the porch as you envision.

  3. #3
    Join Date
    Dec 2007
    Location
    Tennessee
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    Default Re: Pouring New Piers Around Existing Ones

    You should be able to hire a tractor with the post hole digger from a fence company. They may even be able to use the tractor to pull out any existing footers that are in the way, but check on this with them first. You don't want to be paying for a tractor and drive while they sit around and wait for you to dig out the footing(s) by hand.

  4. #4
    Join Date
    Sep 2012
    Location
    Eastern Kansas
    Posts
    104

    Default Re: Pouring New Piers Around Existing Ones

    Keith -- thanks again. On my other post I updated what I found recently. The all-at-once approach seems like I'd have to fully prop up the roof. That's a little unnerving to me! I have a small tractor that might be able to lift about 800# or so with the loader. Maybe I can lift/drag the old piers out with a chain, but they will have to be dug loose. That column is going to be smack dab right in the way of things.

    The soil is pretty loose -- I can probably hand dig a 3' hole in <30 minutes. I have some neighbors around with a PHD if needed.

    Now I have 9 piers total -- 2 corner ones and 7 intermediate. Since they line up "really close" to the columns it would be nice to keep them there, but if pulling out the corner piers is painful, I can see your point about just leaving the old ones alone and pouring a new set.

    It seems like I'd want to pour the piers to the same height, so I can accurately set my blocks and framing so I'm just a bit under ledger height. If not, then I have to shim all that into place. Maybe the tubes would help with that.

    So I think the answer to my question is -- Piers need to be poured in total -- I cannot "enlarge a pier" by pouring more concrete around it. I doubt it -- but I suppose there is the possibility that at the bottom of my 6" piers there is a larger footer. I guess I need to dig down and find out.

  5. #5
    Join Date
    Apr 2013
    Location
    southern CT
    Posts
    15

    Default Re: Pouring New Piers Around Existing Ones

    We have always been able to get 42" down by hand with old porch in tact. its a bit of a pain but not so bad. i would leave the olds and dig new except the corners. Get the appriate hardware for the new posts and you should be all set.
    -Newton Carpenters

  6. #6
    Join Date
    Sep 2012
    Location
    Eastern Kansas
    Posts
    104

    Default Re: Pouring New Piers Around Existing Ones

    Quote Originally Posted by Newton Carpenters LLC View Post
    We have always been able to get 42" down by hand with old porch in tact. its a bit of a pain but not so bad. i would leave the olds and dig new except the corners. Get the appriate hardware for the new posts and you should be all set.
    -Newton Carpenters
    Thanks -- I probably have to support that corner while I dig the pier out, so I need to get some diagonal bracing in. I guess I can dig at an angle so I can get a chain around the old pier. I don't plan on sitting my columns atop the pier this time around, but rather go this route -- http://i49.tinypic.com/35hn720.jpg

    Here is the mess I have -- http://tinypic.com/a/2qvlg/3

    Here are the two corner pics:
    http://tinypic.com/m/fo20sg/3
    http://tinypic.com/m/fo20sp/3

    ..naturally the ones with the most surrounding obstructions.

    Feel free to comment -- good, bad, or otherwise. I'm wide open to ideas and criticism.

  7. #7
    Join Date
    Sep 2012
    Location
    Eastern Kansas
    Posts
    104

    Default Re: Pouring New Piers Around Existing Ones

    What size rebar -- how do I fashion it in the 12" tube? I think I will use 12" tubes -- http://www.menards.com/main/building...469-c-5652.htm -- that will be 36" deep and at the correct height such that either this -- http://www.menards.com/main/building...655-c-5647.htm -- or this -- http://www.menards.com/main/building...657-c-5647.htm -- will get me to the bottom of my framing.

    How do I build the "blocks" at the corner? I was thinking I can sit the blocks (links above) directly on the 12" footer/pier. At the corner, however, 12" diameter is not going to give me enough surface area.

  8. #8
    Join Date
    Dec 2007
    Location
    Tennessee
    Posts
    1,381

    Default Re: Pouring New Piers Around Existing Ones

    12" isn't going to cut it for the line posts either. The blocks are 8"x8"x16".

    I would not use those sonotubes unless the soil is very loose or very sandy. If you have good hard clay, just pour the concrete into the dirt hole. Those tubes in hard clay will always be loose so they do not make good footings.

    You will need to make a square pad for the top 6" of your footings, about 10"x18" for the line footings and 18"x 26" on the corners. Lay rebar across the transition from the round to the square sections so that the square section doesn't end up with a round section punched through it. The square section can go a little above grade if you wish, but if you do, it would look a lot better if it has a finished edge like a sidewalk and not the sloppy "fried egg looking" edges that you usually see.

  9. #9
    Join Date
    Sep 2012
    Location
    Eastern Kansas
    Posts
    104

    Default Re: Pouring New Piers Around Existing Ones

    Keith - thanks. Would the round footer to square pad be done in the same pour? I'm thinking to use the tubes because by the time I get the old footers out the hole could be quite large. I'll know when I try, but I was envisioning having to dig down around most the existing footer and then pull it out via chain on my front-end-loader. That could leave a 12 to 18" hole. It looks like they used a 6" tube the first time. It looks like the top of the "pad" needs to be right about "at grade", as 1 block (8x8x16) and 1 cap (4x8x16) test fit snugly under the old framing before I tore it out. I see your point about getting the footer "close" and then pouring the pad portion precisely the right thickness to set the height. That would be a 2-pour approach right?

    I appreciate the concern for "looks". I should most be ok, here, though as there is good shrubbery coverage all around (which makes working a hassle now).

    I could use some help on how to tie-up the rebar both in the hole and in the pad.

  10. #10
    Join Date
    Sep 2012
    Location
    Eastern Kansas
    Posts
    104

    Default Re: Pouring New Piers Around Existing Ones

    FWIW -- the architecture drawing shows at 24" x 24" x 12" thick "footer" , then a 12" x 12" square pier to near grade, then a pier of bricks above grade to the framing. That's a BIG footer! I don't think I will attempt that.
    Last edited by coloradotrout; 05-02-2013 at 01:24 PM.

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