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The project

I am attempting to bump out a pantry into my garage over my basement stairwell. Including appropriate clearance for the stairway, I will have an approximately 4x3 finished space on a floor of 2x10 joists and 23/32 OSB. I made an exploratory cut into the drywall on the garage side at the approximate dimensions of the pantry door rough opening (See Fig 1). The second cut to the right where I left the foam sheathing in place is intended for access to reroute some electrical wiring.

The problem

The issue I have is with the bracing strap that crosses the planned doorway (it appears to be a Simpson T-Shaped Wall Bracing or similar.)

According to TABLE 2308.6.1 on wall bracing in my local building code (link), where let-in-bracing (LIB) such as metal straps are used, they are required at each end of a wall and not more than 25' apart. What alterations could I make to (re)move the existing strap while maintaining the integrity of the bracing?

Structural context

For additional reference, see Fig. 2 and 3 below of the attic above (the wall in question is the exposed section of studs and insulation.) I do not believe this is a load bearing wall - there is a double header top plate above but there does not appear to be any structural elements connecting this wall to the roof load above (please correct me if I am wrong).

Fig 4 shows wider attic context, the garage is attached and through the hole in the plywood gable can be seen the insulation above the kitchen/living room.

Garage wall Fig. 1 Garage wall

Attic above Fig. 2 Attic above garage wall

Attic above backside Fig. 3 Backside of the above view

Attic above wider Fig. 4 Context for the attic above

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  • Your second picture and your "double header" comment are confusing me. Is that a double top plate on top of the studs? Is that what you mean by "double header"? And for that wedge of plywood above the wall in the second picture, what is that? I would say it's a gable end, but it's edge is sitting on top of the top plate? How is it fastened?
    – popham
    Feb 29 at 4:47
  • Apologies for the confusion; yes, I meant to say double top plate on top of the stud wall. I didn't closely inspect the plywood, I believe it is a gable end attached on top of the top plate via that 2x4 lying on it's short end, and nailed to the diagonals supporting the rafters on the other side. Although I would say this isn't a true gable end as the house continues on the other side. I'll add a picture with some wider context.
    – CGEffex
    Feb 29 at 5:05
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    Yeah, that plywood looks a lot like a shear wall for transferring roof diaphragm load down to your brace wall line, but I don't see the fasteners to complete the load path. Maybe I'm just confused. Maybe the house had an addition. Maybe somebody forgot to install some fasteners. Who knows.
    – popham
    Feb 29 at 5:35
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    I don't expect that the plywood chunk is there for gravity loads. My theory is that similar to my description of the ceiling diaphragm, the roof diaphragm picks up wind load from that same exterior wall, and the strange chunk of plywood is performing the same function as the metal brace below it, transferring sideways loading from the roof elevation down to the wall's top plate. Under this theory the plywood would likely be face nailed to a roof rafter (this roof rafter being another shear collector like the top plate) and face nailed to the wall's top plate.
    – popham
    Feb 29 at 7:50
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    @CGEffex in the future, please be sure to edit clarifications into your original question. Not everyone will read all the comments to find out that when you said "double header" you meant "doubled top plate". I've made the edit for you this time, so this is just a reminder for the next time.
    – FreeMan
    Feb 29 at 12:55

1 Answer 1

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Move the brace to the right so that it's out of your way. It should be inclined at 45 degrees to 60 degrees from horizontal.

Judging from the view in the attic, that's an exterior wall to the left of the brace. As long as the new brace location begins within 12'-6" of that exterior wall, you're within spec. Table 2308.6.3-1 refers you to the brace manufacturer for nailing instructions.

The 12'-6" spec comes from the right-most column of your table. If the center-to-center distance between the two end-of-line braces was larger than 25'-0", then every 25'-0" or less your builder would have installed another brace. Moving the brace to the right will reduce the spacing more still, so the 25'-0" or less spacing spec is still met.

The top plate of the wall is a "shear collector" or "drag strut" that accumulates load from the roof and/or ceiling diaphragms. The metal let-in-braces transfer the load from these shear collectors down to the lower floor. This explains the brace-every-25-feet rule from the code. Each metal brace only has enough strength to transfer 25'-0" worth of drag strut load (the 25'-0" spacing limit also keeps the tension and compression stresses in the shear collector below a threshold). For an end-of-line brace, the brace handles up to the 12'-6" from its exterior wall side, and it handles up to another 12'-6" from halfway to the next brace at 25'-0" or less.

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  • THANK YOU SO MUCH!! You answered my question and clarified the code requirements, which is so helpful. I didn't understand the brace didn't have to run right up against the end of the wall. I reread the last paragraph a couple times, and I am confident I understand that as well. The end-of-line brace handles some of the shear from the exterior wall, but it can be set in up to 12'-6". My thinking was to just remove some drywall and attempt to "angle" the brace up if 60 degrees would clear the doorway. Thank you again!
    – CGEffex
    Feb 29 at 4:57
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    @CGEffex, the load enters the brace through the ceiling, not really the exterior wall. The exterior wall studs span bottom to top, so wind load shows up at the ceiling elevation. From there, load moves to the collector, where the drag strut loading is idealized as a constant pounds-per-foot load pushing the collector to the right or left. For wind coming from the left, the compression in the drag strut ramps up from zero at the exterior wall. At the upper brace connection at something like 10' from the exterior wall, the compression has reached the idealized pounds-per-foot load times the 10'.
    – popham
    Feb 29 at 5:27
  • Makes sense, because the exterior wall can't really put shear force on a wall it directly abuts. Thank you for the clarification.
    – CGEffex
    Feb 29 at 6:46
  • @CGEffex, technically the exterior wall can put shear force on the wall. The maximum brace wall line spacing is 35 ft, though. The exterior wall's tiny 2x4 top plate doesn't have sufficient bending strength to transfer all of that load without breaking. You could make it a great big beam laying on its side, but then your brace wall line would have a giant load concentrated at the end, so your brace line's 2x4 top plate couldn't handle the compression load from that great big beam. Instead, the modern strategy is to stiffen the exterior wall's top plate with the ceiling and roof diaphragms.
    – popham
    Feb 29 at 7:58

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