Why wouldn't the rafters sit directly on the top plate of the wall?

I wonder why they will not be on the top plate also. But you want to handle it kinda like a floor. TJIs with rim board. Set the rafters on top and make a plywood gusset connecting the two. I would also use a 2x4 rat run on top of the TJIs and notch the rafters at the heel for the 2x4.

Sorry to be negative but this sounds unstable and a whole lot of work to make it stable.

The TGI's would need to be 14-16" tall to span the 26'. They need to meet a minimum dead/live load for 'minimum attic storage'. If the rafters and TJI both sat on the top plate of the wall I'd have to cut out the part of the TJI sticking above the roof plane which would affect it's structural integrity. The TJI manufacturers only show this detail using TJI's as both rafter and joist. I thought it might be easier/better/faster? to have the 2x10 rafter sit on top of the TJI joist but I can't find any detail info.

weyerhaeuser has want you are looking for search there site

Sheath your floor.

Use a 2x6 or 2x4 nailed around the perimeter. Birds mouth your rafters to sit on 2x6.

Use a tji trimmer joist that is 1 1/8" to cap your ends of the tji and install squash blocks beside the joists.

Over that span I'd still use tji blocking at center of span.

what do the plans say ?

do you even have plans

Pappagor: Thanks, I'll look at the Weyerhaeuser site.

Shane: That all sounds good. I'm also worried about uplift with this detail, so will probably gusset rafter to joist as Crpntrfrk said.

Use a hurricane tie or twist strap from tji to wall and from rafter to trimmer joist. Or an a35 clip from rafter to 2x6.

Also if you set your trimmer joist flush to framing you can sheath up the trimmer joist and that act as a strong connection from floor to walls.

I would follow Shane O's advice. That sounds like the way I would do it.

Just did a floor/roof detail like this.

Frame as a floor, using rim board. Deck as a floor to tie everything together. Install a bearing plate of 2x4 or 2x6 and birdsmouth the rafter. Wall sheathing should carry across the rim board and tie to the bearing plate to unify the structure. Use a hurricane clip at every rafter to resist uplift. Install clips to exterior to catch full meat of rafter and tie into the sheathed structure.

loneframer: Did you use squash blocks on either side of the TJI's under the bearing plate or did you feel like the rim board with sheathing was enough to support the rafters?

Squash blocks are required at all bearing surfaces. There will be a installation guide delivered with your joists. It will show you how to install as well as typical details for bearing.

Shane O and Lone worded it better but what they have typed out was exactly what I was suggesting.

The rim should be good for about 3000 lb / lf load on it it would be the same as the edge of a conventional floor and no blocks required unless the loads are over that.

haverhillstreet said:

loneframer: Did you use squash blocks on either side of the TJI's under the bearing plate or did you feel like the rim board with sheathing was enough to support the rafters?

Click to expand...

I agree with this post.

CrpntrFrk said:

Shane O and Lone worded it better but what they have typed out was exactly what I was suggesting.

Click to expand...

LVL or Microllam rim.............

Why all the recommendations to birdsmouth over a 2x6? If the rrs align with the cjs, it's not doing anything, except maybe distributing a little load to the rim joist. I'd be fairly concerned though about the rafter-cj connection to resist outward thrust. Check the code tables, you could need 10-20 16D nails here depending on slope and snow load.

http://www.buildgp.com/DocumentViewer.aspx?elementid=4372. Go to page 7, it shows the connection you need, you'll have to sheath before you put rafters on though. You can bevel cut the top of the I joist, just not past the inside of exterior wall.


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The site from Matt0034 was the best I've seen for detailed info.

Knowing my building inspector, he'll want squash blocks irregardless .

I wasn't planning on sheathing the entire attic floor, but it looks like I'll have to in order to achieve the proper rating.

Thanks for all your input. I'm a 'finish'guy, not a framer, and have not done this particular detail before. The way the codes constantly change I wanted to get it right.

Dave