footers ???

Discussion in 'Homesteading Questions' started by MELOC, Aug 22, 2006.

  1. MELOC

    MELOC Master Of My Domain

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    i am getting ready to build my concrete porches to replace old wooden porches. i need some input, answers to questions and maybe links that i cannot find.

    i have not decided whether i am using block or poured walls under the slab. either way, i will make the footers beefy enough to handle either. i know i should put rebar (forget the technical term) vertically under load bearing points and at the corners. my understanding is that 4 pieces are driven in to act as vertical support for the load above and beyond what the footers provide.

    how deep into the ground below the footers should they extend?
    how far into the mass of the footers should they go? to the center?

    i am pretty sure i will use long pieces of rebar placed horizontally and tied onto the vertical pieces to prevent shifting if cracks occur. if my footers are 24 inches wide, how far inside from the edges should they be? how deep should they be...about half way?

    someone posted a link concerning concrete construction but i cannot find that thread. does anyone have a link with specs and diagrams?
     
  2. james dilley

    james dilley Well-Known Member Supporter

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    Footers need to be at least 2' and below the frost line.
     

  3. CatsPaw

    CatsPaw Who...me?

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    'round here (indiana) the frost line is 24". Footers are 24" x 8" deep. Footer is excavated to 32" (placing the top of the footer at 24"). Some people put in rebar, some don't. Never heard of vertical stuff unless you're talking commercial jobs.

    Porches are that heavy.
     
  4. NYSaanen

    NYSaanen Well-Known Member

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    Well now, a 24" wide footer should hold just about anything!!!!

    The general rule of thumb I have always seen is: the footer is twice as wide as the wall is thick, and as thick as the wall. Basically, if you were using 8" concrete block, the footer would be 16" wide, and 8" thick. Rebar in the footer is generally put in the center of the thickness, and two pieces are used, each about a third of the way in from the edge. Some do add vertical rebar sticking out of the footer to tie it to the wall. Depending on the type of wall and what it will support, you may or may not need them. If you end up laying block, if you don't have them positioned just right, it could be a challenge.
     
  5. Farmer Willy

    Farmer Willy Well-Known Member Supporter

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    Correct as stated above. Footers twice the wall thickness wide, wall thickness deep. 2 to 4 (2 over 2 for 10" and 12" commercial type walls) horizontal bars spaced 1/3 apart. The only vertical steel might be stubs of rebar to lock wall to footer if a key isn't formed in top of footer (highly recomend key if pouring wall, 2x4 makes a nice key). Top of footer just under the frost line for your area. If pouring a wall, the verticle steel in the wire could be tied to the stubs in the footer. If laying block wall, short stubs can be burned off with torch or beat down if they don't line up with block core. Same footer dimensions whether it is block or poured.
     
  6. MELOC

    MELOC Master Of My Domain

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    not knowing if i am pouring or using block, i decided to make the footers beefy. i figure a solid poured wall has alot of weight along with a 4" concrete slab and the weight of the roof as well. i started digging the footers last september and ran out of money so they have been exposed for a year. i know that is a bad thing to allow to happen as the soil can get loose and maybe a heavy wall can sink. i thought i had read somewhere that driving rebar vertically in the corners and under the load bearing points, all the way beneath the footers with the footers poured on top of them (minus a little bit that would tie into the footer), can help to keep the footers from sinking.

    also, i decided to make the footers just a bit wider in case i go with block and wish to leave tabs in the joints to allow me to case the block in stone. i could have a little footer left to help support the stone casing.

    any thoughts?
     
  7. Ed Norman

    Ed Norman Well-Known Member

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    I have always heard you shouldn't have rebar exposed outside the concrete, because it will rust and the rust will follow the bar right into the conrete.
     
  8. MELOC

    MELOC Master Of My Domain

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    no rebar outside the crete...maybe some masonry tabs between the joints of the block if i go that route as a way to support stone casing. :)
     
  9. Aintlifegrand

    Aintlifegrand Well-Known Member

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    We poured our footers 16" wide for concrete block. We placed the rebar in the trench horizontally in cradles before the pour.
     
  10. wy_white_wolf

    wy_white_wolf Just howling at the moon

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    Yep. If you want rebar running verticle, you stab it into the footer when it's cured enough to hold it upright,
     
  11. NYSaanen

    NYSaanen Well-Known Member

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    Rebar diven below the footers will do zip for you. Footers are to be placed on solid ground, and it is that which will keep them from sinking.
     
  12. tiogacounty

    tiogacounty Well-Known Member

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    100% correct. There is no reason to drive anything into the ground to attempt to stabilize or stengthen a typical footer or wall. This type of stabilizing is only effective with a pile driving technique using treated wooden poles or steel beams. It is expensive, complicated and involves engineering to determine what is acceptable penetration. No need for any of this on a porch. Also, even though you would have a lot of weight in a poured wall, it is actually very little when figured out in a PSI # on the bottom of the footer. For example my house and full poured 8' tall foundation weigh roughly 244,000 LBS. (I had the house built as a modular and know exactly what each 1/2 weighs, and the concrete is easy to figure) I have roughly 32,000 square inches of bearing at the bottom of the poured footer. So, I have less than 8 pounds of ground pressure per square inch, far less than most folk's have at the soles of their shoes. If you pour a typical 2500-3000 PSI concrete mix, you will be capable of supporting many, many, times the amount of weight that you will be placing on the footer. A lot of typical concrete work done in residential construction is seriously overbuilt. relax, do a half decent job, and it will last for a few hundred years.... Have fun.
     
  13. MELOC

    MELOC Master Of My Domain

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    maybe what i read about using groups of 4 pieces of rebar vertically on the load bearing points, and i cannot find it again, was a remedy for footer ditches that got saturated with rain before they were poured. i think the idea was to get a foot or two below the wet ground into more solid clay to act as a pillar of sorts to help support the footings when poured.
     
  14. tiogacounty

    tiogacounty Well-Known Member

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    Meloc, It's important that any bearing soil be well prepared prior to a footer pour. The trench should be free of loose soil and rocks, frozen ground, standing water and mud. I have spent many hours with a flat shovel cleaning the bottom of a trench out prior to a pour. If you are in a questionble situation, give it some time. Let the ground dry out and shovel all the junk out of the trench and it will be fine. Columns of vertical rod are definitely a common item in commercial pours, they are used to creat posts at bearing points, corners, and for several other reasons. They are not typically used in a poured residential wall. Good luck.
     
  15. MELOC

    MELOC Master Of My Domain

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    thanks tioga...i knew i didn't dream the info...or did i, lol.

    luckily, since the 10-15 inches of rain we had in tropical storm that flooded half of the north east, we have not had much at all. the soil probably is dry now. i may even narrow the 2 foot footer plan a bit to save some $$$.

    i was going to incorporate some tabs/fasteners or whatever the term is as a method of helping to hold a shallow stone casing. i may nix that plan also and live with painted block. i just need to get rolling on this asap.