Mixing lumber with i-joist construction
I’ve been hit a couple of times here at mentioning mixing the use of standard 2X lumber for rim board construction with tji’s. Though there have been some here who have agreed with me that this is really not such a no no.
I don’t claim in any way to have anywhere near the experience and background of MOST of you others here. But I’m involved in a large building project that I’ve taken on more or less for the great fun of it, and some things I’ve done a little differently than the book.
Since the discussions surrounding mixing these building materials has always come out of other discussions, and therefore never been put on the table and discussed head on, I wanted to get some direct feedback on it. What is the big danger? I first found myself building my own rims out of 2X lumber when I found out the insane price of the rims that the i-joist manufacturers wanted to charge. (I’ve since been informed of the LVL that’s available but simply hadn’t heard of it before yesterday). I thought it then suddenly made sense to me why they urge us not to use anything but what they have to sell.
So I guess my question is, on outside walls .. where the floor stops and there is no ‘beyond’ that point .. why is it so damn wrong to use a rim made of lumber. I’ve been constructing sort of ‘headers’ to go on my outside walls: 2 2X10’s on edge with periodic 3X material inside to keep the 10’s exactly 2 1/2″ apart thereby creating a long ‘header’ that is exactly 5 1/2″ wide and 9 1/2 inches tall since I run a quarter inch ply ‘bed’ across the top for the subfloor to sit on. This does not even come into contact with any tji’s and it is strong enough to support some heavy walls that I’m using above. The only thing I’d really have a question about is that I also used, this time, 2X10’s on edge to ‘meet’ the tji ends at both opposite walls, nailing through them into the flanges. Here .. I could see how shrinkage could be a problem… but even so not necessarily.
But overall it seems to me that an eighth inch shrinkage here and there … why such a problem? .. we mix and match shrinkage prone and non shrinkable materials here and there all the time in building.