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Thread: Beam sagging

  1. #1
    gary Guest

    Default Beam sagging

    I have a 6x6 dimensional beam that spans 12'. It is in the basement, supporting floor joist that span 7' and one story above on one side, and 7' and 1 1/2 stories on the other side. It is sagging about an inch in the middle. I thought I would sister a 2x6 micro-lam on each side of the beam, once it was jacked up to level. Would this work?
    What is the best way to sister the micro-lam, nailing or bolting through?

  2. #2
    Mike Lewis Guest

    Default Re: Beam sagging

    Gary,

    Assuming that the micro-lam has the same modulus of elasticity as the dimensional beam, the ratio of new deflection to the old deflection will be the same as the ratio of the old beam width to the new beam width. For instance, if the old beam is 6 inches wide and the new beam is 10 inches wide then the new deflection will be 6/10 of the original deflection.

    As for how to attach it, I think nailing would probably be best only because you are not removing material from the beam.

    If you want to reduce deflection, you get your best bang for the buck by adding stiff material to the top and bottom surfaces of a beam.

    Mike Lewis

  3. #3
    Mike Sloggatt Guest

    Default Re: Beam sagging

    Gary -
    I personally would Through bolt 2 1/2" x 5 1/2" steel plates to either side of the beam with a 2x6 on the outside of each beam . The 12' seems like a long run for a 6x6 - Perhaps someone removed a supporting column?

    MPS

  4. #4
    Billy Guest

    Default Re: Beam sagging

    i agree with gary

  5. #5
    bill burns Guest

    Default Re: Beam sagging

    I am with mike sloggatt on this one. plates on each side .
    figure you have 252 square feet of floor loading on this plus whatever roof area( you don't give roof pitch and height or number of layers on roof). this is a lot of weight for essentially four 2x6's to support over 12 feet!.
    I would be willing to bet one or more posts have been removed.
    anyway, get some calculations done to do this right. cheap insurance now .
    are you in snow area??

  6. #6
    George Roberts Guest

    Default Re: Beam sagging

    Like everyone else, I think the beam is a bit shallow. Adding more 2x6's seems like a waste.

    A rough estimate (clearly wrong because of lack of information), indicates that a 6x10 beam should have been used to meet code requirements.

    I would support either steel and/or sistered deeper (2x12 ??) timbers or another post.

    It might be worthwhile to have an engineer compute what you need.

  7. #7
    Stephen Beaty Guest

    Default Re: Beam sagging

    Just something to keep in mind - When you double the width of a beam, you double its strength. When you double the depth of a beam, you increase the strength fourfold.
    Stephen

  8. #8
    mike maines Guest

    Default Re: Beam sagging

    Gary, if height is a problem, I would suggest using a "c" channel steel beam. Installs just like a steel plate, but like Mike Lewis said, you need more material at the top and bottom. Through-bolt with more bolts toward the ends of the beam.

    If height is not a problem, your idea of jacking the beam and sistering on engineered lumber would work well. If you can support the ends of the new beam, 20d spikes are probably enough for attachment. If you can't support the ends of the new beam, use lots of bolts--again, more toward the ends of the beam.

  9. #9
    Jen Guest

    Default Re: Beam sagging

    Seems to me you had a peir removed. Most block, bein 7 1/2 inches wide, yer really defeatin the purpose but addin a microllam without any bearing.
    Althought, it does help, don't get me wrong...it seems that would just be a quick fix, bolted or nailed. I'd sugest jacking up the beam and addin a new pier, maybe even so much as extra block on both sides of the original piers, then bolting your microllams to the original beam.

  10. #10
    TODD Guest

    Default Re: Beam sagging

    IF YOU WANTED TO FIX AS IF IT WAS INSTALLED PROPERLY IN THE FIRST PLACE YOU MIGHT CONSIDER SHORING THE FLOOR JOISTS ON EITHER SIDE OF THE BEAM. PROP THE BEAM,AND CUT IT OUT IN SECTIONS.PRIOR TO THIS YOU WILL HAVE TO CHOOSE A NEW BEAM STRUCTURE,WILL YOU BE POSTING IT OR NOT.I WOULD TRY TO USE AN 8 INCH STEEL I-BEAM IF POSSIBLE,CREATE A NEW POCKET IN THE FOUNDATION,HAVE THE STEEL BEAR 4 INCHES ON THE FOUNDATION SO YOU CAN SLIDE IT IN,PLATE THE STEEL,AND GET SOME YOUNG DUDES TO HIKE IT UP INTO THE POCKETS.AFTER THAT I WOULD POST IT IN THE CENTER AND RE-CONNECT THE FLOOR JOISTS WITH RAFTER TIES. IF STEEL IS NOT AN OPTION,THEN PERHAPS A THREE PLY 12 INCH LAMB-BEAM INSTALLED SIMILAR.HOWEVER, I WOULD PROTECT THE ENDS FROM THE MOISTURE THEY WILL RECIEVE FROM THE FOUNDATION

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