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.
Thank you.
Replies
I would suggest putting this question under "Building Techniques" rather than General Discussion. It is, after all, EXACTLY about BT.
T.
Thanks. Will do.
Yeah, maybe should be under construction techniques.
Anyway, from a technical point of viiew, the rim joist keep the joists from rolling, so blocking will perform the same function.
On the other hand, you have the joist manufacturer and your local code to contencd with.
The joist manufacturer will give you a lot of free engineering if you buy their product. You might want to give them a quick call, or talk to the folks where you plan to buy them.
It's not all that unlikely that this very question comes up often enough that they have something they can fax back to you in like 10 seconds.
"Let's get crack-a-lackin" --- Adam Carolla
The main function of the rim board is to support the weight of the bearing wall above.
In this case, the studs go down to the sill, so that's not an issue.
Hey Boss, I always though the rim kept the joists from trying to roll.
The joists are already made to hold the distributed load of the wall above, no?
I see it's a concentrated load in a sense, but the weight of the wall is distributed over all the joists.
Am I getting my apples and oranges confused?
Edit: on further thought, maybe it doesn't matter 'cause the alternative to the rim joist is solid blocking between the joists, which would serve both functions, but I'm still curious.
"Let's get crack-a-lackin" --- Adam Carolla
Edited 4/22/2006 9:49 pm ET by philarenewal
I spoke with a rep from Biewer, TJI company that has been supplying our I-joists lately and he said the same thing, the rim takes on the weight, kind of like a header he said. In a TJI system with point loads, the OSB will act like a knife and split the flanges in a I-joist. Making it useless.
I-joists can't handle much of a point load. That's why squash blocks are required at interior walls where another bearing wall is stacked above it. The plywood web is thin, and doesn't have much crush resistance. If all you needed was to keep the I-joists from rolling, the rim boards wouldn't have to be more than 1/4" thick.
From the moment I picked your book up until I put it down I was convulsed with laughter. Some day I intend reading it.
Thanks to you and Stilletto for the clarification.
Just when I think I've got it figured out, there's MORE. ;-)
The good thing is full depth blocking will act as squash blocks, but I am obsessed with knowing what all the pieces are doing.
Thanks again.
"Let's get crack-a-lackin" --- Adam Carolla