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  1. #1
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    Default Span of metal I-beams? - manuf home

    Have inspected a pretty fair share of manufactured homes, but they have always been on crawlspace type foundations. This one was set on top of a walk-out basement.

    Question: what is the maximum unsupported span for a 8" metal I-Beam?
    This is a double-wide manufacture home, so figure 25 feet wide. Beams are spaced about 10 feet apart.

    When I see something similar that has been set on a crawlspace foundation, there is at least one, usually two pier supports under each metal I-beam, beside the ends of the I-beams resting in foundation wall notches.

    The basement of this manufactured home is partially finished, but from what little I can see, there appear to be 4x4 posts supporting only two of the 5 beams, and not on center. The seller supposedly had to have an engineer's report done for their bank loan (I haven't see it yet), but my gut tells me the report and any work done was bogus (I don't see any tie-downs either). The attached picture is showing one half of the basement (there are 'finished' bedrooms to the left of the space in the picture).

    I will not attempt to calculate the engineering specs, but was curious if anyone had any rough span tables for metal I-beams?

    Thanks
    Terry

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  2. #2
    James Duffin's Avatar
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    Default Re: Span of metal I-beams? - manuf home

    It seems you would need to know the weight of the load for a span table to mean much.


  3. #3
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    Default Re: Span of metal I-beams? - manuf home

    I have several span tables - for lumber and TJI's, not metal.
    Was hoping for some general guidelines. I'm referring the buyer to the seller's engineer report, and based on that, recommending further evaluation.

    HUD has foundation specifications for manufactured homes
    Permanent Foundations Guide for Manufactured Housing

    I breezed through it again pretty quickly, but it only seems to deal with crawlspace sets. A lot of it deals with tie-downs. The HUD booklet specifically leaves out basements and metal I-beams even though I would have thought it would be the same weight load calculations.


  4. #4
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    Default Re: Span of metal I-beams? - manuf home

    25' seems a bit much generally for an 8" I beam. On blueprinted jobs I usually see 15-20 at the most. However the important factor when dealing with I beams is the weight designation of the beam. The same height, length I beam comes in different weights. W15, W20, W25, etc. Each weight category has higher load limits.
    When I was dealing with I beams more I would measure the thickness of the beam and call a guy I knew at a local steel shop. He would tell me the probably W of the beam. Not 100% accurate with using a tape measure to check but it helps to know somewhat at least. Consider asking the builder what W the beams are.

    www.aic-chicago.com
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  5. #5
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    Default Re: Span of metal I-beams? - manuf home

    I can't answer the question, but have a couple of comments I have to make.

    The stud wall appears to be supporting the beam to some extent, although it should be braced. I would like it to have plywood screwed to one or both sides, but I'm not an engineer.

    The metal frames the two halves are built on add a lot of stiffness so they distribute the weight lengthwise. You have steel beams running both ways. However, they are not welded together and there's a lack of bracing there. I told you I couldn't answer the question.

    John Kogel, RHI, BC HI Lic #47455
    www.allsafehome.ca

  6. #6
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    Default Re: Span of metal I-beams? - manuf home

    You need all of the dimensions of the beam before you can use the tables, but the 1993 AISI tables can be found on the internet. A quick Google search yields
    http://www.toolbase.org/PDF/DesignGu...SpanTables.pdf


  7. #7
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    Default Re: Span of metal I-beams? - manuf home

    All the information you need will be available from the manufacturer. There should have been cut-sheets for this particular home as part of the installation details. That said, I know of no manufacturer that does not call for lally column support at the center span of each transverse beam-included will be the required structural weight bearing charcteristics of the colmuns. Of course, those columns need to be supported by footings and not just the concrete floor. What is commonly missed in these installations, is solid blocking between the transverse beam and the band-joist of the marriage wall. Ten foot spacing of the transverse beam is not uncommon, I have seen 12' (rarely), but 8' to 9' is most common. But again, the manufacturer will specify the maximum allowable spans. The home's carriage beams should be fastened to the transverse beams, (either mechanical or welded) and the transverse beams should be fastened at the foundation wall and also at the lally columns.

    Last edited by Gregory Booth; 11-26-2010 at 12:46 PM. Reason: missed punctuation

  8. #8
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    Default Re: Span of metal I-beams? - manuf home

    Looking at the photo again, the wall on the left is at the center-line? Are the requisite columns inside that wall?


  9. #9
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    Default Re: Span of metal I-beams? - manuf home

    Quote Originally Posted by John Kogel View Post
    I can't answer the question, but have a couple of comments I have to make.

    The stud wall appears to be supporting the beam to some extent, although it should be braced. I would like it to have plywood screwed to one or both sides, but I'm not an engineer.

    The metal frames the two halves are built on add a lot of stiffness so they distribute the weight lengthwise. You have steel beams running both ways. However, they are not welded together and there's a lack of bracing there. I told you I couldn't answer the question.
    Hi John in regards to the stud wall it seems to me like a partition wall not a supporting wall. Also to the left there seems to be rafters on the ajoining room to which they can attach a ceiling. any extra support they supply is always a good thing. the studs are not directly under the beams so maximum support is not the intent there it seems. Always good to hear other opinions even if they can't nail everything togethere get's us all thinking.

    just my 2 cents


  10. #10
    Bruce Adams's Avatar
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    Default Re: Span of metal I-beams? - manuf home

    Terry
    I have seen this several times in this area. Both on basement and crawlspace where the home has been installed on a permanent foundation. There usually is a center beam with support post. and the home is required to be fastened to the foundation with proper ties. Usually requires an engineers stamp. Never seen an installation instruction by the manufacture. Banks in this area require an engineer to sign off on them at time of each sale. Did one three time over the years and the third engineer would not sign off until additional support was installed. Most of these have been close to the lake.
    The center wall in your photo is not a support wall. If it were a support wall it would have to be covered on one or both sides.
    Bruce


  11. #11
    Leigh Goodman's Avatar
    Leigh Goodman Guest

    Default Re: Span of metal I-beams? - manuf home

    (there are 'finished' bedrooms to the left of the space in the picture)

    Do these "bedrooms" have the required exit to the exterior? If not you should inform buyers.


  12. #12
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    Default Re: Span of metal I-beams? - manuf home

    I'm wondering whether that framed partition wall might be intended to be bearing. Looking at the photo again, notice how they used a 4x4 under the RSJ and the doubled stud at the opening is likewise conveniently located under the RSJ? There should be design documents detailing loads and whether any support mid-span was indicated.


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