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Converting non-structural end truss to structural?

h4x | Posted in General Questions on

So, I goofed and failed to order my end trusses with structural webbing for the shear wall…they currently only have 24″ OC webbing for attaching sheathing and are not structural ends. 

Before I jump down this rabbit hole, am I crazy for thinking that I can add additional webbing (both vertical and diagonal) to “make” it structural?  My thought was that I might have to add vertical bracing so that it is 12″ OC…not ideal, but I don’t want to deconstruct my trusses either (ordering new trusses is not an option)…then add additional diagonal webbing as necessary?

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Replies

  1. Expert Member
    MALCOLM TAYLOR | | #1

    h4x,

    The engineering for your trusses was done by the supplier. They are the only ones who can perform, or approve you to perform, changes to them.

    Your other option is to discard the gable trusses and frame the gable ends as stud walls. You would have to find out from whoever designed your shear walls whether the gable ends have to be framed out of continuous stock, or can be interrupted by the top plates.

    1. h4x | | #2

      Hey Malcom,
      I'm currently working with the truss supplier to look at options.

      In the meantime, I'm trying to identify other potential options. Along these lines, framing out the gable ends is the predominant plan. I'm hopeful that we can simply add the additional bracing to the gable trusses, but this may be wishful thinking. To explain that a little...my thought was that--all things being equal--if we are using the appropriate connectors/fasteners, that we would be able to place additional vertical webbing (and diagonal where needed) to account for the necessary fastener requirements on the sheathing to make it a structural wall, and then properly secure it to the building shear wall to transfer wind loads. This is essentially what we would be doing if we were to frame out the gable ends, right? We're looking at that option because the framing requirements are insufficient...granted, there are considerations for the top and bottom plates of a structural wall that will need to be considered as it relates to the top and bottom chords of the truss...but if we are considering framing out a gable end in order to get structural stud placement, then couldn't we do the same thing by adding the appropriate bracing to the truss? As it stands, the truss has framing @ 24" OC...a gable stud wall would be 16" OC, right? If we add bracing to the truss, then we would be looking at 12" OC, which, while not ideal, should technically be more supportive than 16" OC.

      So, like I said, I may be over simplifying things...but it would seem that the major considerations are going to be frequency of stud placement for the shear wall, and then appropriate connectors for the new (and potentially existing) webbing to make sure it is rated for the wind loads.

      Nothing is set in stone at this point, and I'm just spit balling ideas right now...thanks for the input thus far.

  2. Expert Member
    MALCOLM TAYLOR | | #3

    H4x,

    The problem is that without knowing the requirements of the shear wall, you are just guessing. Maybe the existing gable truss is just fine? Either way, there is no advantage to making the gable truss load-bearing by adding diagonal braces, as it bears on the wall below whether it is a shear wall or not.

    The place to start is determining what the shear wall requirements for the gable wall are. What are the requirements for the wall below the truss? What is the fastener pattern, and what is the spacing of the framing behind? Where did you find out you needed a shear wall there, and who designed it?

    1. h4x | | #4

      Doh! Talk about putting the cart before the horse...thanks, I start there and run those calculations.

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