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Diagonal blocking similar to let-in bracing. Considering removing or alternatives.

Discussion in 'Residential Structural Codes' started by tssop, May 28, 2019.

  1. tssop

    tssop Registered User

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    I am a homeowner doing a minor remodel of my new 60's single-story rambler. I drew and submitted plans to the city, and they reviewed and approved the plans.

    One of the changes is a new window towards the corner of the house in a bedroom. It is a tall but narrow window (30x72), with the first king stud located 2' 6" from the corner of the house.

    I am doing demo, and have run into a series of diagonal blocks running from the ceiling to the floor in this corner in the way of the new window opening. I am familiar with let-in bracing for shear strength, but this seems different as it is not "let-in" to the studs, rather mitered pieces of 2x4 nailed between each stud. I always thought the strength of diagonal bracing like this came more from it being continuous, and am curious how much this blocking is actually doing.

    I can find an engineer to consult if needed, but wanted to see what people here thought of how effective of a roll this is playing as it stands and perhaps how advisable or not it would be to remove. It seems what is there already wouldn't meet prescriptive code for a shear wall.

    I am also planning an addition on this end of the house for next summer. The addition would make this no longer a corner and I believe make the shear properties of this segment of wall less important. I don't want to do something unsafe with the guise of "I'll fix it later", just wanted to mention in case it factors into the discussion.

    Appreciate any thoughts you have!

    [​IMG]
    [​IMG]
     
  2. TheCommish

    TheCommish Sawhorse

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    Unless you are in a seismic zone propose continuous wood sheathing on the inside and put extension jambs on the window trim
     
  3. ICE

    ICE Sawhorse

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    Assuming that the plans were approved without mention of the blocking or a need for a shear wall it should be okay. It is worth pointing out that just adding wall bracing accomplishes little unless the braced wall segment is restrained top and bottom.....to a degree that keeps it in place during an event.
     
  4. Mark K

    Mark K Platinum Member

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    Let in bracing can actually reduce the lateral strength of a wall.

    What is shown is typical of much older construction.

    The diagonal bracing shown is actually not very effective. It is not clear how one would calculate any strength it would provide in compression and would not be effective in tension.

    The straight sheathing shown has minimal capacity. Older is not always better.

    With the addition of the new windows I would look very carefully whether some additional lateral strength needs to be provided.

    Since you are planning an addition I would talk to an engineer now in case it would be beneficial to do something now that would benefit the future work.
     
    ICE likes this.
  5. mark handler

    mark handler Sawhorse

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    Untitled.png
    Diagonal bracing assist in Plumbing and Aligning walls during framing
    Diagonal bracing assist in preventing racking
    Diagonal bracing assist with tension and compression of walls in a wind or seismic event.
     
    #5 mark handler, May 29, 2019
    Last edited: May 29, 2019
  6. mark handler

    mark handler Sawhorse

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    One way to keep the frame aligned, is to plywood the wall, inside or Outside.

    Make sure you insulate the wall
    Make sure you extend the Electrical Boxes if plywood is installed on the inside.
    Also looks like you are missing Anchor Bolts...
     
  7. tssop

    tssop Registered User

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    Thanks all for the feedback! It looks like plywood could be a viable option, though I don't have access to the sill plate from the inside of the house, just the bottom plate of the studs. I was also wondering about a product like Simpson's wall bracing (WB/WBC line) further inside along the wall as I could actually get that down to the sill plate from the inside and would be easier to install. I would have room for that about 10 feet in along the wall from the outside corner of the house.

    I am also considering just waiting until next year when I re-side the house along with the addition. I could sheathe the outside with plywood, which would I think solve this issue. If I go that route I'll just have to deal with storing an extra window for that time.

    I am aware of the lack of anchor bolts, that is another project I will address shortly.

    I have reached out to a few engineers in my area, we will see if any of them want to consult with me on this.
     
  8. tssop

    tssop Registered User

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    Follow up: I am reading about braced wall panels in the IRC, and it looks like according to R602.10.2.2, a braced wall panel must begin within 10 feet of a braced wall line. Though I'm still learning the terminology, I believe the previously pictured corner of the house would be the start of the braced wall line. The rightmost edge of the right window gives me *just* enough room to fit in a braced wall panel.

    It also appears that the Simpson WBC bracing, installed in an 'X' would be acceptable here as it is allowable in-lieu of let-in bracing. This would by far be the easiest for me to install and would not conflict with the window position.

    Still may get an engineer to consult.
     
  9. mtlogcabin

    mtlogcabin Sawhorse

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    That is what I would do since you cannot use the sill plate from inside the house
     
  10. ADAguy

    ADAguy Sawhorse

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    Consider introducing Simpson hold-downs on either side of window framing and adding plywood between?
     

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