I-Joist Rafter to Wall Framing Connection 1

[Sokka10]

Hi everyone,

I'm currently drawing some generic details for future use. One of the details I need is where an I-joist is used as a rafter and connects to the wall framing. Where I am contractors almost exclusively use I-joists for roof rafters instead of dimensional lumber. I have seen details that other engineers use, including my old firm, and they all specify that either a Simpson VPA connector or a beveled plate is to be used for the rafter to bear on. If a VPA connector is used then my question is moot. But, if a beveled plate is used then there are a few issues that I can't answer to my satisfaction. I have yet to see one of these details where the connection from the beveled plate to the top plates is specified. If the rafters are at a steep pitch, say 10:12 or more, then that beveled plate will be quite thick and I don't see how to connect it to the top plates without some very long screws.

Second question is that on these typical details I've seen, a Simpson H1 or H2.5A clip is specified for the rafter to attach to the top plates at the outside of the wall. See the drawing below. The H1 and H2.5A clips cannot be bent so I don't think they will work in this application. Should they be placed on the inside of the wall and nailed into the beveled plate? You think that's ok? I would feel ok with that if I could come up with an adequate solution for attaching the beveled plate to the top plates.

To summarize...

1) How to attach the beveled plate to the top plates? Super long screws? LTP angles? A35 clip?
2) How to attach the rafter to the beveled plate/top plates? H1 or H2.5A on the inside and nail into the beveled plate?

Thanks!

 

[jayrod12]

I would say the clip should be on the outside face unless you take into account a significant reduction in capacity. There's a technical bulletin put out by Simpson on this reduction and ways to restore full capacity of the hold-down. The shouldn't need to be bent to connect to the rafter there but I'm thinking of the H3 or H4 type holdown. I don't see why it would be an issue for the other style holddowns.

 

[Tmoose]

The attached image shows a Canadian I-joist supplier's details.

Weyerhouser has a free guidebook but I don't feel like creating a user account to download it.

 

[Sokka10]

Thank you jay and Tmoose. I had a brain fart with the clips. I was thinking that the shear blocking would interfere with the H-clips but of course the H-clips would be installed before the blocking. Duh.

Tmoose I've looked at quite a few details like that from various suppliers but none of them show a recommended method of attachment for the beveled plate to the top plates. I'm sure the contractor usually ends up nailing the crap out of it down into the plates but I'd like to put something on my detail that works well. On a 10:12 pitch the tall side of the block will be nearly 5" tall. Even 16d nails (3 1/2" long) would barely penetrate into the top plates if they are installed closer to the shorter side of the block

 

[Mike Mike]

Sokka -
1 - plate to plate connection - any of your suggests would work fine for transferring uplift and in-plane shear. another possibility is toe screws.
2 - joist to plate connection - yes, your suggestion would work fine. another idea is to screw the joist bottom chord down - no nails or clips required.

jayrod - thanks for pointing out the tech bulletin, looks like Simpson determined top plates roll at only 165 plf.