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Thread: Load weight/deflection question

  1. #1
    Associate Engineer
    Join Date
    Oct 2021

    Load weight/deflection question

    Hello from definitely a NON-engineer!

    I am fixing a 60' single wide mobile home that had a sun room attached along the 60' length. They share a common wall but there is now an 8' opening and a 3' window, both of which only had 2"x4" headers that are beginning to sag.

    I would like to open this up now to a 20' opening, which would probably involve 2"x6" or 2"x8" headers or double headers to hold up the weight of the roof (trusses and decking and asphalt shingles), BUT this will lose a LOT of headroom as the walls are not very tall.

    So I would like to use metal instead (a small i-beam or c-channel or something that will not bend) and not lose too much headroom. Maybe a 4" c-channel with small legs or ???

    The original mobile home just had 2.5" wooden jambs around a 30" door (no big deal), but I would like to expand this opening considerably now to 15'-20' if possible and affordable.

    Thanks so much for helping me figure out what product and shape and material and thickness to buy! Hopefully something stocked locally. And whoever comes up with the best solution will hear a really good engineer joke form me (yes another)!


  2. #2
    Principle Engineer
    Join Date
    May 2015
    You have not provided enough information to allow an engineer to find a solution.

    As you might imagine, the width of the trailer will impact the weight of the roof and any snow load applied to your beam. There is also a condition question because you noted “sagging” in some areas and previous modifications – suggesting hidden problems.

    But let’s guess that this is a 12’ wide trailer. You could find a span table that suggests a 5-1/8” wide x 15” deep glu-lam would be in the ball park for a 20’ span. Please note, this is just a starting point for calculations not a definitive answer.

    What is going to support each end of the beam? Three or four 2x6’s on each side of the opening might support it when sistered together and tied to secure headers and sill plate (can’t be sure what you’ve got there). And then there is the question of what is beneath the floor to support the load of the two columns on either side of the opening. The trailer floor was likely designed for a distributed load not the concentrated load of a column. That too needs to be considered. Did the wall help carry some of the floor load initially? You have a floor engineering problem to consider as well as the roof beam.

    It is hoped that you can begin to understand why your question can not be answered in an on-line forum. Safety is not a laughing matter to engineers.

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