this post was submitted on 09 Sep 2023
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I don't see floor trusses used too often so it's neat to see them here
It’s used so the other trades don’t wreck all the TGIs by putting incorrect penetrations. It has all the holes they could possibly need, but sometimes they’ll stick cut a plate….
Holy shit this explains so much!
Our dishwasher in a 2010s era home finally died, and when we pulled it out to install a new one there were these off center holes behind it!
Like, wtf? Why did you need three holes for one cord?
I guess during construction different people thought it wise to drill different holes for different things?
The answer is capitalism. Doing things the best way and most profitably is not always the same.
This is interesting. I did my garage from the studs out. Using conduit to run electrical never even occurred to me. I think it would be a real bitch to drill holes through each stud level enough to push a rigid conduit through. Maybe there are some flexible conduits, but now you're taking a 1/2" hole and making it a full inch, in a 2*4, which is nominally 1 and 3/4". But now I'm thinking they did it with Bx, and maybe I'm not fully versed on why. I know the shielding acted as a ground as well.
I'm rambling. I think there's some rationale that's not just capitalism=bad. Code is okay with running straight Romex through studs, so long as you staple and whatnot. Maybe it'd be above code to use conduit, but I think it's just a lot of extra work for not very much payoff. So yeah, capitalism=bad, I guess.
So during my garage retrofit, I did run, in addition to 100amps for a panel, a separate conduit with two Cat6s. In the event of upgrades in tech, I can easily pull that through and replace with Cat7 or whatever. I won't, but I could. It's about 90ft from the house to the garage.
Laziness more or less.
It's easier and cheaper to just run one wire. Most people don't want more than a couple different port locations so why bother?
And you're not installing the other two items so it's not your responsibility. You're also not going to get paid more for doing the extra work. Even if the homeowner was the one paying you, most aren't willing to pay a bit extra just so it's easier on the next guy.
How are floor trusses different from regular floors? What are TGIs and incorrect penetrations?
Thank you if you have time to answer.
There isn’t really any type of “regular” floor in wood, but the 3 most common are dimensional lumber (2x10s for example), engineered joists (TJIs which are dimensional top and bottom chord and OSB web) and engineered trusses (what you see here, dimensional chords and webs.
I apologize for that typo, it’s TGI I-Joists, explained above briefly. The incorrect penetrations can happen in either dimensional joists or engineered joists. The easy rule of thumb is no more than 1/3 the diameter of the material (9” joist being 3” max) and has to be in the inner 1/3 (9” again so no holes within 3” of the top or bottom of the joist.
Now most engineered joists come with pre penetrations and any deviation without their express consent can void their warranty, BUT following general guidelines shouldn’t lead to any issues.
I'm seeing them more and more, which means OSB is probably too expensive to use for engineered trusses now.
It’s a trade off, more expensive, but you’re not replacing them because some trade made an incorrect penetration.
Basically you’re paying more to prevent issues later.