Cantelevered Rim Joist that's load bearing

[Rich Zimmerman]

Quick question for ya'all. Here's the framing plan for the shed-style roof I'm working on

So we've got a a 3-4' overhang all around. Not a big deal. Rim joist connection is generally pretty irrelevant in that it's not really holding much (if any) load. EXCEPT for the part labeled (in red) A and B, we've got a floor to ceiling window, so I can't put a header under there. That's why I've doubled the 3 joists around the opening and then the rim becomes structural, picking up the ends of the joists that are no longer cantilevered over the window opening. So I'm wondering what the proper detail is for these connections? Generally web-stiffener and face mounted bracket for the single joists (I would think), but for the double joists the load is actually UP, so do you mount the bracket upside down? Is that even an approved Simpson methodology? Is there a better way to make these connections?

NOTE: The part labeled B is actually a bit different than A. In B I put a header in the roof over the windows because picking up that huge span seemed a bridge a bit too far for the rim. Of course that means that the steel post there in the corner that has to support two beams AND a triple I-Joist, all in the same plane is going to be pretty tricky.

 

[Rich Zimmerman]

So looking at the load charts I can probably get by with a BA or HB bracket nailed to the nines, but it still seems the RIGHT way to install this would be a lower capacity hanger installed upside down. I can't find anything on the Simpson site that allows for this though. Any thoughts?

 

[KootK]

I do the upside down hanger thing pretty regularly in this situation. Of course, you've got to pick something that also has enough capacity for any uplift. My preference is a header over the window for the following reasons:

- Something solid to attach the window to. Granted, blocking does this too.

- I worry about field QC when it comes to complex hanger installs.

 

[Ron247]

I would use the upside down hanger too, but as KootK points out, I have had trouble actually getting someone to install them that way.

I use upside down hangers in several ways but I have had to put a note on my drawings similar to this: "Hanger to be installed upside down as shown. Engineer did not make a mistake when drawing this detail. Install upside down even if you do not know why."

 

[slickdeals]

Depending on the loads, you can perhaps use a conventional hanger that has uplift capacity. There's a lot of Simpson hangars that have decent uplift capacities.

 

[NorthCivil]

I'm fully on board with the upside down hanger deal. Any connection capacity in the simpson catalog should be valid in any direction, I figure.

I would connect all the joists to the rim joist with hangers right side up, and connect the triples to the rim joists with hangers upside down. vice versa would be acceptable as well. the triples and the typ joists should have hangers installed opposite eachother

If you wanted to get fussy, those 2 joists that land on the triple in the outside area, you could rotate 90, so that no gravity load will be imparted on the triple, which will load the upside down hanger the wrong way. (theoretically). in practice, this is probably negligible.

what piqued my interest more is your reference to "triple I joists", I've never gone down that road, nor seen anybody else, is it a valid solution? seems a bit odd. usually I'll just spec an LSL/PSL/ built up LVL

 

[Ron247]

NorthCivil, I do not think hanger loads are the same in any direction. One direction has the seat taking load and the other direction does not. If they publish a gravity load and an uplift load separately, you can "flip" the load capacities.

 

[Rich Zimmerman]

NorthCivil, you're right about the triple I-Joists. I was thinking about doing something funky there because the topmost beam doesn't really need the extra strength till it gets to the cantilever and rim, so I was thinking about trying to put in something where two of the three I Joists actually don't extend the whole length, but stop maybe half way back. Plus it's a hold over from before I put the header in over the windows. Likely a double I-Joist can handle the load there (have to run the calcs). The one a bit lower should likely be switched to a LSL/LVL or glu-lam.

 

[HouseBoy]

I use hangers installed upside down often so... I'd go along with that notion as others have.

Sometimes (if I'm concerned about the whole thing staying together well) I specify tension connectors strategically located to improve the way that the rim is anchored to the rafter or joist ends.

 

[NorthCivil]

@Ron247,

thats what i was getting at - if simpson publishes a capacity for a hanger, flip that hanger upside down, and the capacity applies for a force applied upwards

in engineering, clear communicating is the most important part- cheers

 

[CANPRO]

I’ve used upside hangers before in a similar situation where I wanted to support the rim joist by the end of the joists.

Simpson shows the allowable loads relative the beam/joist orientation...as far as I know there is no mention of the global orientation - same capacities should apply to the upside down hanger.

 

[Ron247]

Sorry NorthCivil, guess I misunderstood.