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Can I support an extra 10 inches of sub floor overhang with 2x10 angle pieces bolted to the side of a joist? It'd be a 6 foot run. I figure I'd space the angle pieces 10 to 12 inches apart and secure them together with 2x6s in between laid horizontally in between. I need to extend a non structural wall so I can extend a bathroom wall out approximately 10 inches.

If you look at the picture I added to this post, I'd basically do that.

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Side A would be the joist and side B would be my sub floor

isherwood
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Justin
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  • Unfortunately I don't have the room to add a joist. So basically where Sides C and B meet I'd have the non supporting wall. If I add another joist, I'd lose head clearance for my stairs leading up to my second floor. – Justin Jan 29 '23 at 21:34
  • Would probably not pass code. It probably will stay up with a short wall that has extra nails/screws holding it to the ceiling joists/blocking. Those angle pieces will not have too much weight holding ability, compared to joists/blocking. – crip659 Jan 29 '23 at 22:32
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    If you're trying to support a wall, you'd probably need an "Upset Beam" - basically a joist mounted at floor level **above** the floor, supporting the bottom of the wall (so it, or bossibly they, vanish in the wall structure, visually. Obviously the end area needs support blocking at regular joist level. Trying to hold a wall up with an angle bracket is just going to twist the joist it's attached to. – Ecnerwal Jan 29 '23 at 23:23
  • _Can this be done?_ Sure. _Will this be sufficient?_ Oof, I wouldn't think so without some serious engineering analysis. Even if the new wall isn't load bearing, just the lumber & drywall are going to be _heavy_ and that's going to provide a lot of lever force on whatever fasteners you use to hold your little angle brackets on. The braces may not break, but you're likely to pull screws or nails right out and have the whole thing fall straight down. – FreeMan Jan 30 '23 at 12:45
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    "Non structural wall" is evasive here. I think the intent is to suggest that the floor should support only the weight of the wall itself, and nothing above it. But what you really want is to build a *non structural floor*. Really? What if someone later places a bathtub against your new wall, with feet on your non-structural floor? What if they hang a wall-mounted double vanity on your wall? What makes a wall non-structural is that it is not *currently* supporting anything else, not that it is *incapable* of doing so! – jay613 Jan 30 '23 at 16:13

1 Answers1

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No.

Any cantilever needs a 1:3 overlap ratio at minimum. That means a girder joist inside the existing floor three times the overhang depth, a beam at (underneath) the edge of the existing floor, and perpendicular joists. You cannot apply twisting forces to the rim joist as you propose.

Even if you fully boxed the existing joists against twist, you're relying on fasteners in tension. That's rarely allowed. You need direct bearing and fasteners working in shear. The fact that you're triangulating with the subfloor is irrelevant. That's not a structural technique any inspector would allow.

I suggest that your reformulate your question to ask how to solve your problem rather than posing the XY question you have now.

isherwood
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