Really, this is for BossHog…stupid question, but it’s up your alley, so to speak.
Wandering around our new neighborhood, lots of houses under construction…all with either Ijoist or the truss style floor joists, and as I wander around, it brings up a question.
Most of the truss style floor joists have a sold section at each end (see attachment if it worked). On one job in particular (probably due to poor planning), I see that this section is being cut off, in some cases almost entirely, to make things fit.
What purpose does this solid end section serve? I should rephrase that. I understand the need for a solid web member at the end of the truss… why is it of varying lenghts? The length seems to be unrelated to anything else…..
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Since Boss is on his donut break, I'm going to jump in with a guess. It functions as a squash block, and a starting-ending bearing for the web members. Note: I know even less about trusses than I do about electricity.
Whenever you are asked if you can do a job, tell'em "Certainly, I can!" Then get busy and find out how to do it. T. Roosevelt
The solid end is called a "trimmable end".
I wouldn't say these trusses are cut off due to poor planning. There's more to it than that.
For starters - You can use a trimmable end (TE for short) when you don't know the exact span of the truss ahead of time.
For instance - I use them a lot on 45° bays. I can lay a bay out on paper and tell you to .0001" how long it should be. But anyone who's framed a house knows you can't build to tolerances like that. So the TE allows you some "slop" when you're building the trusses. And the end of the truss can be cut off at 45° to match the angled side of the bay.
Another area this helps in is stairs. We have a heck of a time pinning guys down to EXACTLY where they want the stair openings. The TE allows us to make the trusses a little long so they can be cut to the exact length once they're set.
There are companies out there who stock floor trusses with TEs on them. The theory is that you can just go buy some 24' floor trusses and cut them to fit. But adding the TEs is expensive enough that this isn't widely done.
Is that more than you wanted to know?
When vultures are on their deathbed, are they ever tempted to eat themselves?
Guess I'll add trusses to my list of things to avoid talking about.
Are you saying that it's ok to cut off the entire TE? Which brings up another question...is it permissible to trim floor trusses that don't have TE's?
Whenever you are asked if you can do a job, tell'em "Certainly, I can!" Then get busy and find out how to do it. T. Roosevelt
"Are you saying that it's ok to cut off the entire TE?"
Every trimmable end detail I've seen allows for the whole TE to be cut off. You do have to be sure to leave the vertical in place that just after the trimmable area. But it would be worth asking the specific manufacturer about their trusses.
"...is it permissible to trim floor trusses that don't have TE's?"
Yes and no. Sure you can cut them. But you're supposed to get an engineer to review what you've done, and specify a field repair. This typically involves adding some new webs, then gluing and nailing some plywood on the sides.
That's why the trimmable end is a good idea in some situations - It's a lot easier than doing a field repair.hy are builders afraid to have a thirteenth floor but book publishers aren't afraid to have a Chapter 11?
More than I wanted to know? Not on your life!!! That's exactly what I wondered....and, in fact, I was looking at an area around a stairwell which is why I thought of the question in the first place.
Thanks, Boss!
No problem - Glad to contribute something useful to the forum once in a while.
Seems like my views on trusses are more welcome than my political views.
(-:I'd rather vote for what I want and not get it, than vote for something I don't want and get it. [Eugene V. Debs]
Ran across this picture - Is this like what you saw?
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See if the law benefits one citizen at the expense of another by doing what the citizen himself cannot do without committing a crime. Frederic Bastiat's test for immoral government acts
That's the kind of thing I was talking about. Trimmable End makes sense....thanks for the info.