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Thread: lally columns

  1. #1
    DIY Junior Member
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    Default help..lally columns

    I want to replace a lally column in my basement. the columns are spaced about 5'5" apart and i want to take out the center column (of 3). My plan was to take 2 more columns and place them just inside of the 2 outer ones, on top of these columns I would put an 8x8 beam to span the 10' gap that existed. My main beam consists of 6 2 x 12's. I have lot of people telling me that leaving the 11 foot gap would be fine b/c of my existing beam, and that i dont have to put anything there at all, but i think just to be safe the 8x8 supported by the 2 columns will make up for the absence of the middle one i pull out. will my plan work?
    Last edited by smatarazzo; 09-14-2009 at 02:32 PM. Reason: needs new title

  2. #2
    Moderator & Master Plumber hj's Avatar
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    Default lally

    Are you going to take the advice of someone who has NEVER seen your installation, and has NO IDEA why the lallies were installed that way? It seems so unusual that there may be some good reason for it and the only way to be sure is to have a structural engineer check it out.

  3. #3
    Extreme DIY Homeowner Scuba_Dave's Avatar
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    Doubling the span distance without knowing the load on the beam is not a good idea
    If the exisiting beams could span 11' they would have probably built it that way
    As hj said, you can't guess at this, you need to have an engineer verify the loads & beam required
    DIY Handyman (not 4 hire)
    I have enough to do to my own house

  4. #4
    I&C Engineer (mostly WWTP) Lakee911's Avatar
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    Post details about your house, spans, materials, walls, loads, etc and someone can help.

    6-2x12's seems like a fairly large beam to me...must be a big load...

  5. #5
    DIY Senior Member seaofnames's Avatar
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    As stated. Get an engineer to look at it.

    Then get an engineered beam!! Much stronger than just 8x8 or 6 2x12s or any of that jazz. Engineered beams are the way to go for any kind of major structural change.

  6. #6
    I&C Engineer (mostly WWTP) Lakee911's Avatar
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    If it indeed has that sort of load, I would put in a steel beam probably.

  7. #7
    DIY Senior Member seaofnames's Avatar
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    Quote Originally Posted by Lakee911 View Post
    If it indeed has that sort of load, I would put in a steel beam probably.
    I didnt even think about that!! Steel is awesome.

  8. #8
    Mechanical Engineer loafer's Avatar
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    By doubling the span, you will decrease the stiffness of that beam by a factor of 8.

  9. #9
    I&C Engineer (mostly WWTP) Lakee911's Avatar
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    Quote Originally Posted by loafer View Post
    By doubling the span, you will decrease the stiffness of that beam by a factor of 8.
    If it doesn't fail first...

  10. #10
    Mechanical Engineer loafer's Avatar
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    Quote Originally Posted by seaofnames View Post
    I didnt even think about that!! Steel is awesome.
    Well, if we assume that the 6, 2x12 beam is required over your 5.5' span for stiffness purposes, then it is fairly easy to calculate the required steel beam that will span 11 and still meet the same stiffness requirement. According to my figures, I come up with a W12x35 beam as a suitable replacement, which is a wide flanged I beam that is 12 deep and weighs in at 35lb/ft. Other steel beam options are possible, providing the minimum moment if inertia of 285in**4 is met.

    My calculations are based on maintaining an equivalent stiffness from the 5.5 span to the 11 span. In other words, if your existing beam has a deflection criteria of L/500, the maximum deflection is 0.011in, the same deflection criteria at the 11 span will allow for a 0.022in deflection.

    I would not start this project w/o first having an engineer come out and look at your particular situation though.

  11. #11
    General Contractor Carpenter toolaholic's Avatar
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    Take this with a grain of salt . Bolt 2x8 channel iron on either side of the beam
    Place 1/2" bolts 32" on center staggered. One up one down. Now You've increased the point load on the column footings. This is My 49 th year building homes. You need and experienced carpenter , a structual Eng. and a building permit. But that ain't gonna happen,is it? If this don't work out SUE DUNBAR,
    He's the only one who has any money here!

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