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My house in Northern California has a gable roof. In the attic, there are two 2x4 angle braces (one at each gable end) that connect from the ceiling joist (gable-end) to the ridge board (mid-span). Please see photo to understand what I mean.

What is their purpose/name? Can I can do something with them since they cross the attic space and reduce head space. Thanks

Attic brace

Attic brace

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  • these angle braces can be replaced by bracing the rafters instead
    – Jasen
    Sep 15 '20 at 5:23
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    @Jasen wouldn't a brace tied from the wall to a rafter instead of the ridge still take up head room? Also, wouldn't there need to be some calculation to ensure that the wind/seismic resistance of the new brace(s) be proper to meet the local codes? I understand you made a "comment", not an "answer", but new folks often don't understand the difference and may take what you've said at face value and run with it...
    – FreeMan
    Sep 15 '20 at 10:54
  • If you hit your head on them, wrap them with padding, perhaps brightly colored padding, or mount lights on them or something. Having the roof collapse is not a good thing, so living with them is your better bet. If you are trying to make the space livable/finished, put a wall around them.
    – Ecnerwal
    Sep 15 '20 at 12:30
  • yes, if you use a 2x4 it would take up 2" of head room. (the brace goes diagonally across the rafters starting in the corner ending at the ridge). if you use steel strapping it takes less headroom, but you need longer braces that cross I posted a comment because I don't have the resources here to compute what would be a suitable replacement
    – Jasen
    Sep 15 '20 at 23:03
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It’s difficult to see, but I suspect your gable end wall is not ballooned framed, but rather has a double top plate. This creates a “hinge” in the wall.

The diagonal braces keep the end wall from bending like a hinge during a wind storm or seismic activity. (I know, you’re going to tell me the ceiling will keep everything square and plumb. However, ceilings can’t give you a load resistance value to maintain the wall.)

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  • Commonly known as a ...Wind Brace.
    – Ecnerwal
    Sep 15 '20 at 12:25
  • Understood and will leave them there. Maybe I could make it stronger with an X pattern (add another 2x4 on the other side) or add another secondary/shorter brace along the existing ones. Thanks
    – Son Nguyen
    Sep 15 '20 at 14:22
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Get a framing manual for you location at look in the chapter on bracing and/or stick-built roofs,

You can get the equivalent shear resistance by bracing the rafters on both sides with the same sized lumber. you'll have to cut the brace where it crosses the underpurlin. And it'll need to be fixed to every rafter (some of which will be hard to reach) and to the underpurlin and the ridge board, and you'll need 4 braces instead of two so you'll end up using more wood)

there may be a way to use steel strapping instead of wood, you'll need to check the framing manual.

Some disassembly may be required to fix the corner ends.

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