This is a fairly basic question, but I don’t do much framing, so:
When TJIs are going to be supported by a flush beam of dimensional lumber, what’s the best practice method of aligning them?
I think I remember reading once that since the dimensional lumber will shrink, the TJIs should be initially set a little bit low. That way, after the flush beam shrinks, all the tops will line up.
So how much offset is required for something like a 4×10 or 4×12? 1/8″?
If my recollection about this is entirely wrong, please let me know.
Edited 5/23/2007 5:50 pm ET by Ragnar17
Replies
I'll set dimensional lumber a hair high to an engineered beam.... for shrinkage. But your situation is bassackwards from that scenario.
Can't say I've ever hung I's from a dimensional beam though. I'd say set them flush and make sure your 3/4" decking spans over the beam... no joint on or within 12" or so of the beam. Then it shouldn't matter if and when the dimensional beam shrinks.
Can't say I've ever hung I's from a dimensional beam though.
I'm assuming from this comment it would be better to avoid the dimensional lumber altogether! What would you suggest?
Edited 5/23/2007 6:02 pm ET by Ragnar17
LVL or glulam.... whatever is common for your area. It's usually best to not mix dimensional with engineered lumber whenever possible. It happens all the time (although usually opposite your situation) but it's not really "best practice". View Image
Why use dimensional lumber and not use lvl's? Even if it's specked dimensional lumber you can call the Architect up and ask him to change it to lvl's and you don't have to worry about any of this.
I see no reason to worry about it. Shrinkage will be minimal in any event. Follow the advise above and don't splice your subfloor over the beam. If the beam shrinks, the gap will be under the plywood. Don't set your beam higher than the joists, this would be creating a hump that may or may not go away. Align the tops and forget about it.
Span across the beam with your drywall, (just as you've been advised to do with the subfloor) and don't fasten the drywall to the beam. This will eliminate and screw pops or cracking at the beam.
We'll just avoid using dimensional lumber -- problem solved.
Told you this was easy! ;)
Thanks to all for the help.