TJI Joist layout

[Structeng_1414]

Hi, I am trying to lay out joists for some non-orthogonal walls. These will be top flange hangers to top plates of the bearing walls. My question is, would you lay it out at a similar angle to both walls (parallel to the exterior wall here), or with 90 degrees to at least one wall?

Thinking for constructability it might be easier to have 90 degrees to at least one wall, but I really don't know if it matters. It also will end up at a weird angle to the exterior wall so might have to do a beam across with infill like this?

 

[phamENG]

First, why hangers to top plates? Are these fire walls? This whole thing would be a lot simpler with them bearing on the walls.

If you have to use hangers, I'd go with the same angle everywhere. Good chance those are going to be custom hangers, so you might as well make them all the same angle to reduce fabrication costs. If they're not custom, then having only one hanger type will a) potentially provide volume purchasing discounts and b) reduce the chances that they'll use the wrong one.

 

[Structeng_1414]

phamEng, that's a great point. This used to be 2 stories and we were doing a modified balloon framing situation, so I had it in my head that these were hangers. But this is now the roof, so they could absolutely just bear on the walls.
Is there any issue with skewed joists bearing?

 

[ChorasDen]

Is there any issue with skewed joists bearing?

For the joists themselves, no, they just require 1.75" of bearing and lateral restraint from rim or blocking at end bearing conditions. I could see some difficulty with the roof sheathing layout if you frame perpendicular to the exterior walls. is that center wall a shear wall, and you can treat each side as a separate diaphragm tied off to blocking in the middle?

 

[DoubleStud]

Yeah, you dont want to use hangers if you can avoid it. I agree with phamEng. Most of the adjustable skew hangers don't have very good capacity. Plus you need blocking if you use I joist.

 

[phamENG]

If those are the only two areas you're doing it, making it 90 degrees will make blocking and shared bearing easier over the central wall.

 

[jayrod12]

I'm also a proponent of the third layout where after the last full length joist, or double joist, you flip the orientation and block that last bay to the outside wall. The loading from the wedge can't be too much more than a standard joist space, therefore I don't necessarily see the need for a beam.

The reason I would be preferring this option, we always provide blocking in the last joist space towards an outside wall, with the first layout you show, you would still need to do that. So why have a short joist if you can just do it all with blocking pieces. It would also avoid having a stiffer joist right next to a softer one (i.e. a short one right next to a long one).

 

[KootK]

I also like #3, particularly if you line the framing up across the interior wall for sheathing convenience. The turned framing obviates the need for the blocking that you'd probably want up against that wall anyhow.

 

[RontheRedneck]

Another vote for #3.

It's always easiest to have a straight wall to pull the layout from And a straight wall perpendicular to the I-joists to start the plywood layout. Bu this can be done with a little effort.