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    Concrete footings for new basement support columns

    Asked May 23, 2009, 08:23 AM — 8 Answers
    I'm replacing the support columns under the main beam in a small cape cod. I just wanted to run my footing plans by everyone so I know if I'm making any glaring mistakes. I've cut open the existing slab and dug 18"-square x 19" deep holes for the footings and adjustable monoposts (see attached pic).

    - Is rebar even required? I don't believe it is, but plan on adding anyway. Are (2) 'X'-patterns 3" up from bottom and down from top good, or would a different pattern be better?
    - Is the 3/4" gravel required for drainage? These posts are in the center of an existing poured slab, so I'm not sure water will even get to them.
    - Are (2) anchor bolts enough in the bottom plate, or should I go with (4)? There will also be a 2nd concrete pour to cover the adjusting screw.

    Thank you to everyone for any input.

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    8 Answers
    21boat's Avatar
    21boat Posts: 2,441, Reputation: 212
    Ultra Member

    May 23, 2009, 11:58 PM

    Linfield Pa. If you are going to use rebar which really is overkill here for a 12" thick pad. Box the rebar not criss cross.

    Also you don't want to have any crushed stone under that pad at all.. Its not a drain issue and where would it even drain too???

    12" thick create is also over kill Normally the pads are 24"x24" and 8" to 10" of concrete. It's the width of the pad that carries the load ( spreads out the load) not the thickness

    Thick is to keep it from breaking under compression and THEN spread out that load.

    2 bolts are fine. Its just to stop any shear movement.
    LinfieldPA's Avatar
    LinfieldPA Posts: 32, Reputation: 3
    Junior Member

    May 25, 2009, 05:51 AM
    Thanks 21boat. I should have asked BEFORE I dug the holes - now I'm going to have monster footings! I guess if I ever want to add 3 more floors, I'll be safe! ;)

    FYI, I tried to rate your answer, but AMHD won't let me because I guess I rate you too often (because you answer so often!). Anyway, I greatly appreciate your response. Hopefully I can get them all poured today. Thanks again.
    21boat's Avatar
    21boat Posts: 2,441, Reputation: 212
    Ultra Member

    May 25, 2009, 09:56 PM

    I answer a lot because of doing so many trades on a weekly basis. Keeps me from getting bored.

    Glad to help out..
    iam5050's Avatar
    iam5050 Posts: 7, Reputation: 2
    New Member

    Jun 21, 2009, 02:11 AM

    This is right up my allley... I am in the process of redoing by basment.. I don't want anything fancy, but the slab is very lets say un-even and wavy and also thing very thin...

    I am in my house for at least a few more years but cannot walk away from job not done the right way... What would you all suggest my next move to be?

    PS... there are a lot of small cracks in the floor which I was going to silicone then paint... Water seems to be burping its way through this... Seems like the only right thing to do is start for square one... Not sure I have the time or budget...

    What would you suggest ---- and what would pour mans verdict be?

    ballengerb1's Avatar
    ballengerb1 Posts: 27,379, Reputation: 2280
    Home Repair & Remodeling Expert

    Jun 21, 2009, 09:36 AM

    You can't paint silicone but there are other sealer that can be painted.
    21boat's Avatar
    21boat Posts: 2,441, Reputation: 212
    Ultra Member

    Jun 22, 2009, 06:32 PM

    the slab is very lets say un-even and wavy and also thing very thin... there are a lot of small cracks in the floor... but cannot walk away from job not done the right way...
    Ima 5050

    Sounds like the right way is to pour a new concrete floor. Lets see

    We have

    Wavy floor
    Thin floor
    Lot of small cracks
    Water burping its way through.

    I say fix the water problem burping through and remove old floor. Stone it right and drain tile it and vapor barrier and Crete.

    If this shows up when you go to sell, (the disclosure act in the selling info can get serious. ) As a buyer I would low bid on the asking price to allow me enough money to fix the floor...
    Jkelly830's Avatar
    Jkelly830 Posts: 1, Reputation: 1
    New Member

    Feb 20, 2013, 01:47 PM
    To Original Poster:

    How did the job go? I noticed in your drawing that the post is constructed with(4) 2x10's , not (3) as written. Which did you go with.

    Also, I am not an engineer, but I didn't think your footing was overkill in any sense. I think it was smart - based upon what I have seen structural engineers design for similar residential homes in my area.

    Good Luck.
    wayne1yahoo's Avatar
    wayne1yahoo Posts: 11, Reputation: 1
    New Member

    Feb 20, 2013, 05:30 PM
    You need to go to your local building code people by online or in person. They will give you the code specifications needed for your locality. You do normally require rebar in the footings concret

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