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what size i beam for garage

mhaag66 | Posted in Construction Techniques on August 8, 2009 08:40am

Does anyone have a link to span tables for I beams.  I am wondering what size beam I need to span 33 feet in a garage to eliminate any posts. The garage is 24 feet wide. and the roof is 4/12 asphalt with 3/4 sheeting.  the walls are cement block. the rafters are 2 feet apart.  currently there is a wood beam that mainly consists of a 6×6 beam with one post in the center.  the garage was a stable in its earlier life.  any resources would be greatly appreciated

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  1. User avater
    BossHog | Aug 08, 2009 08:44pm | #1

    To fgure a beam size you need to know the loading. Since your profile isn't filled in and you did't say where you are, you could be in northern Canada or southern Florida.

    In the beginning of a change the patriot is a scarce man, and brave, and hated and scorned. When his cause succeeds, the timid join him, for then it costs nothing to be a patriot. [Mark Twain]

  2. gfretwell | Aug 08, 2009 09:16pm | #2

    I had and engineer spec an 8" 34# for a 25' span with only the second floor load on it (not roof). It wasn't enough. The floor was still springy.
    33' is going to be a huge beam. Taller is better than heavier (something I wish my engineer had mentioned)
    If you go 10 or 12" tall you don't need as much meat in the steel.
    If you reduce the joist span by using two beams you get a stiffer floor too. (another thing that went unspoken).

  3. Piffin | Aug 08, 2009 10:34pm | #3

    One heck of a lot larger one than you imagine. 33' is a long span

     

     

    Welcome to the
    Taunton University of
    Knowledge FHB Campus at Breaktime.
     where ...
    Excellence is its own reward!

  4. User avater
    jonblakemore | Aug 08, 2009 10:49pm | #4

    What kind of depth do you have to work with?

    A 14" beam will be a lot more manageable and perform better than a 10" beam. Don't take those numbers as meaning anything- they're just off the top of my head.

     

    Jon Blakemore

    RappahannockINC.com Fredericksburg, VA

  5. FastEddie | Aug 09, 2009 04:33am | #5

    If the garage is 24' wide, why do you need to span 33'?  Do you mean you need a 33' beam with 24' between supports?  Actually if that's the outside dim of the garage, your span is less than 23'.

    "Put your creed in your deed."   Emerson

    "When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it."  T. Roosevelt

    1. Framer | Aug 09, 2009 08:12pm | #26

      If the building is 24'x33' and the beam is just going to hold up ceiling joist for attic space, he can just run a I-beam or properly sized lvl or glulam the 24' way and run two small lvl's the 16' way butting into the 24' beam on each side to hold up the ceiling joists.

       Joe Carola

  6. DanH | Aug 09, 2009 04:44am | #6

    If the garage is 24 feet wide, why do you need to span 33 feet?

    As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz
    1. fingersandtoes | Aug 09, 2009 06:14am | #7

      My take is that the garage is 24 x 33. The beam is a ridge beam supporting the roof rafters.

  7. Framer | Aug 09, 2009 06:46am | #8

    If it's a 24'x33' garage, why not run the ridge beam the 24' way and the rafters run the 33' way? You obviously want a full cathedral ceiling and have a choice which way to run the beam, no?

     

    Joe Carola
    1. gfretwell | Aug 09, 2009 07:21am | #9

      If this is single story new construction, why not just use trusses?
      I was thinking this was carrying a second floor.

      1. Framer | Aug 09, 2009 07:52am | #10

        If this is single story new construction, why not just use trusses?

        Sounds like a one story garage and he wants a full cathedral ceilings. In order to get thast you need a structarl beam. Using scissor truasses gives you a lower ceiling.

        If the main picth is a 6/12, then the bottom of the scissor trusse I think would be arouind 3/12. This is why scissor trusses are no good if you want a high ceiling and if you are limited with height restictions scissor truuse won't work that well.

        If he doesn't care about a full cathedral, scissor trusse will work fine.

         Joe Carola

      2. bd | Aug 09, 2009 01:32pm | #13

        Why not read the original post? It's not new construction. The garage is a converted stable.

        1. DanH | Aug 09, 2009 03:06pm | #16

          I didn't miss that. But the guy's talking about essentially reconstructing the garage (or at least the roof), so there's no reason to be constrained to simply replacing the existing beam.
          As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz

          1. User avater
            BossHog | Aug 09, 2009 03:44pm | #17

            Sixteen replies, and the OP hasn't come back to read any of the messages. Makes me wonder if we're all wasting our time...
            He's not dead, He's electroencephalographically challenged.

          2. DanH | Aug 09, 2009 04:37pm | #18

            > Makes me wonder if we're all wasting our time...You're on BT and you gotta even WONDER about that???
            As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz

          3. ruffmike | Aug 09, 2009 08:20pm | #28

            I think Dan deserves an award for this one. http://forums.taunton.com/tp-breaktime/messages?msg=123181.19

                                        Mike

                Small wheel turn by the fire and rod, big wheel turn by the grace of god.

            Edited 8/9/2009 1:21 pm by ruffmike

          4. runnerguy | Aug 09, 2009 05:43pm | #19

            I thought the same thing. So to save MY time I'm recommending a W36X300. Ought to cover it.

            Runnerguy

          5. FastEddie | Aug 09, 2009 06:04pm | #20

            You want that galvanized?"Put your creed in your deed."   Emerson

            "When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it."  T. Roosevelt

          6. runnerguy | Aug 09, 2009 06:23pm | #21

            Just to be safe, that's probably not a bad idea. Also, I was figuring on 50ksi steel but everybody probably assumed that.

            Runnerguy

          7. frammer52 | Aug 09, 2009 06:28pm | #22

            Just to be safe, that's probably not a bad idea. Also, I was figuring on 50ksi steel but everybody probably assumed that>>>>>>>>>>>>>>>..

             

            >G<

          8. Piffin | Aug 09, 2009 07:45pm | #24

            Now we got a problem with headroom, LOL 

             

            Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

          9. PedroTheMule | Aug 09, 2009 11:00pm | #33

            Yo Piffin,

            Now we got a problem with headroom, LOL

            Headroom, headroom we ain't got no problem with headroom....walk in the room and bang you head all day long! With that level of steel he shouldn't ever have one single problem with knocking it out of place.

            Pedro the Mule - & he can use the little stars he creates to light it up at night

          10. Piffin | Aug 09, 2009 07:44pm | #23

            He never mentioned reconstructing roof or anything else, just wants to get rid of the post 

             

            Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

          11. DanH | Aug 09, 2009 09:30pm | #32

            He didn't mention it, but he's talking about it.
            As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz

      3. DanH | Aug 09, 2009 03:04pm | #15

        That's what I was thinking -- trusses. Or even a 24-foot beam or two supporting a longer beam the other direction.
        As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz

  8. Engineerguy | Aug 09, 2009 11:26am | #11

    Span tables for steel beams are in the Steel Construction Manual.  I think they are up to the 13th addition now.  There is the short answer to you primary question.

    Long answer is that if you change the load path, as you are indicating, you will also need to change columns to support the beam, as well as new stem walls/footings due to the additional loadings.  And not knowing your locale, soil, snow, seismic and wind loading allowances may need to be taken into account, which may require additional lateral bracing, especially for such a long span.

    Recommend getting a local engineer to assist you with this.

     

    I think I can say, and say with pride that we have some legislatures that bring higher prices than any in the world. - Mark Twain

  9. Piffin | Aug 09, 2009 12:48pm | #12

    "currently there is a wood beam that mainly consists of a 6x6 beam with one post in the center. the garage was a stable in its earlier life."

    A bunch of you guys just missed the boat on this one by not reading the OP

    It is NOT new construction

    It is NOT a ridge beam

    It is NOT running in the 24' direction

     

     

    Welcome to the
    Taunton University of
    Knowledge FHB Campus at Breaktime.
     where ...
    Excellence is its own reward!

    1. fingersandtoes | Aug 09, 2009 09:15pm | #31

      "currently there is a wood beam that mainly consists of a 6x6 beam with one post in the center. the garage was a stable in its earlier life."

      "A bunch of you guys just missed the boat on this one by not reading the OP"

      The descriptoin is a bit vague, but I see it as a 4/12 roof with the rafters supported by an old 6"x6" beam. How is it not a ridge beam?

      1. Piffin | Aug 10, 2009 12:18am | #34

        Well, with all the work I have done on old places, I have never once seen a 6x6 ridge beam, so I was picturing it at the ceiling level.You are right, he neither specifies, not rules out that it is the ridge beam. If that is the case, it could be even easier than I imagined to run the steel 24' direction 

         

        Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

        1. fingersandtoes | Aug 10, 2009 02:06am | #35

          No I can't say I've ever seen one either. You are probably right. I don't think I have the slightest idea of what's going on here

        2. User avater
          Jeff_Clarke | Aug 10, 2009 03:31am | #36

          Methinks the 6 x 6 is at the ceiling level (reading between the lines that aren't there).

          Jeff

  10. Piffin | Aug 09, 2009 02:14pm | #14

    There may be a way to re-engineer this whole thing fairly easily to use a beam in the 24' direction, but would need several photos top show the current layout and structure before I could sketch up a solution.

     

     

    Welcome to the
    Taunton University of
    Knowledge FHB Campus at Breaktime.
     where ...
    Excellence is its own reward!

  11. User avater
    Jeff_Clarke | Aug 09, 2009 07:49pm | #25

    More info please - 24' deep x 33' wide?   Attic storage? (or not)  Habitable space above?  (or not)  Snow region?   Roof load?  etc.

    You're likely going to be in the W12x26 or W12x40 range, depending upon some of the above and deflection criteria.

    You'll need 3 1/2" or 4" lally columns at both ends with suitable foundation/footing bearing - keep that footing in mind (you're not going to sit on slab/block).

     

    Jeff



    Edited 8/9/2009 12:51 pm ET by Jeff_Clarke

    1. Piffin | Aug 09, 2009 08:17pm | #27

      I was thinking more like W14x38(36) but we know nothing about upper storage and snow loading 

       

      Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

  12. sisyphus | Aug 09, 2009 08:31pm | #29

    Based on the original post he needs a beam that will span 33 ft to carry a load that a 6X6 can carry over 16.5 ft. (Assuming there are no point loads involved?)



    Edited 8/9/2009 1:32 pm ET by sisyphus

    1. Piffin | Aug 09, 2009 08:34pm | #30

      True, but if you are reverse engineering it, you need to know if that 6x6 is White oak, Heart Pine, or spruce, and whether it was sufficient or is in failure. 

       

      Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

      1. sisyphus | Aug 10, 2009 04:11am | #37

        No question that the OP should provide more information. It did say that the structure was stable previously which could imply that it has gone awol since but I took it to mean that the beam (as you say wood species unknown) had been sufficient. Whether it met code or best practice is, of course, another story.

        1. fingersandtoes | Aug 10, 2009 10:07pm | #41

          Was a stable. Is unstable.

          1. sisyphus | Aug 11, 2009 06:26pm | #43

            "Was a stable. Is unstable."

            You're right I missed the "a" when I read the first post.

  13. Snort | Aug 10, 2009 04:55am | #38

    We just built an attached 36' x 24' garage w/storage above. Engineer speced two sets of double 18" x 24' LVLs, evenly spaced, for the main beams.

    http://www.tvwsolar.com

    We'll have a kid

    Or maybe we'll rent one

    He's got to be straight

    We don't want a bent one

    He'll drink his baby brew

    From a big brass cup

    Someday he may be president

    If things loosen up

  14. MattSwanger | Aug 10, 2009 02:18pm | #39

    in my pea sized brain me thinks maybe a few girder trusses supporting the ridge and bearing on the walls would be best. 

    Woods favorite carpenter

     

    1. Piffin | Aug 10, 2009 07:00pm | #40

      You got some good darn peas in that pod of yours 

       

      Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

  15. Piffin | Aug 11, 2009 12:25am | #42

    We're wondering if this thing fell down on your head yet?

    but even if you've vaporized, it's been an interesting discussion. Thanks for teasing us into it.

     

     

    Welcome to the
    Taunton University of
    Knowledge FHB Campus at Breaktime.
     where ...
    Excellence is its own reward!

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