I am rehabbing an historic 1895 wood frame building. I want to replace the entire first floor structure with I-Joists. All the sills have been replaced. The I-Joists will sit on the new 4″ x 6″ sills. The problem is that the building is balloon construction, and the existing wall studs sit directly on the sills. Hence, I cannot use a Rim Board in the typical fashion. If a Rim Board were to be used, it would have to go on the outside of the studs in lieu of the exterior sheathing. However, the Rim Boards are much thicker than the sheathing, creating problems for the water table trim and clapboard siding. The I-joists can be anchored to the sills in the normal fashion, but I am not sure how to anchor the tops of the joists. Can I use 3/4″ plywood sheathing instead of a Rim Board, or blocking between the studs and the I-Joists? Any suggestions? I am not so concerned about structural integrity as I am about meeting code (Massachusetts) and Boise-Cascade requirements. I have not seen anything about using I-Joists in old construction. Note: This same inquiry is posted under “General Discussion” also. Thank you. |
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Great question. I would think that you could set I-joists on the sills next to the studs, and then block between them, pushing the blocking out against the sheathing. The other thing you'd probably have to do is add fireblocking right on top of the I-joist flanges. I'd talk to the inspector about this before doing anything, or maybe get an engineer to draw a detail for you.
I did exactly what you are asking on a job about 5 years ago and put blocking on top as Dave said.I don't see why you can't use I-joist blocking in between unless your inspector doesn't allow it. On new construction you can. Once the I-joist is nailed to the sill, I would nail through the stud and into the top of the I-joists and then nail the blocking in. You really have no other choice. All I-joists I've ever used you can't use 3/4" as a rimboard.
Joe Carola
Edited 4/22/2006 8:20 pm ET by Framer
I think you might be able to pull it off too. The rim board is engineered to pick up some of the load from the walls above, but since you're balloon framed I would think that the only load on the joists is the actual floor load. I'd probably add squash blocks to the ends of the joists myself as cheap insurance, but that may not even be necessary.
Diddo... The rim is to help with loads from the walls.
Your walls are bearing on the foundation. You could hold your I-joists back the thickness of the rim and run rim board blocks which would give you the top nailing to your I-joist.
Howie