I-Joist or TJI?
Pardon my ignorance, I’m just a simple home owner here and occasional DYI.
Anyway, I’m having an addition put onto my house (no, I’m not doing it myself–WAY out of my league).
The architect had specified 9 1/2″ TJI to span the addition (it’s approx. 37′ long and 25′ wide. Joists are running parallel to the 37′ run).
Anyway, my question is, in the plans, they spec out TJI, but in the “first page” of the architect’s stuff, it says they can use I-Joist or Trus-Joist.
It looks like they used I-Joists (what clued me in was that there were no pre-drilled holes, as I was expecting an “easy” run for the electrical).
What’s the difference between I-joist vs. TJI? Other than the pre-drilled holes?
Do they both have the same structural support?
I believe they are using IPI-800’s and the specs were for TJI 230’s
Did you say your 9 1/2" joists are spanning 37'?
Not the whole length.So they ordered 2 diff. lengths.The first is about 16' and that goes onto a microlam beam that runs the width (about 25').Then, that leaves a span of about 22'.However, there's a load bearing wall that moves in a bit, so the 22' I-Joist gets support at the Microlam at one end, and 10' and 14' for the "next" support, and then it continues on to the exterior load bearing wall.
Whew! I thought you were clear-spanning that monster.
Without digging through data readily available on the joist manufacturer's website, my simple answer is that yes, the two products are interchangeable.
BUT, there's so many different web depths and flange widths available that you need to do the research to see which 'models' are equal across different manufacturers. What usually happens is this: architect specs a specific brand. Contractor takes the plans to his local lumberyard. They say, we don't stock brand X as specified, but we have brand Y that is compatible. Contractor would then get architect approval for the change. Very simple. Happens every day with everything from structural lumber to windows to bath fixtures.
Don't worry too much about the holes. Go to your manufacturer's website and read or down load the simple installation booklet they provide. It will tell you where and when you can and can't drill through the webbing of your joists. You can do some pretty amazing things with I-joists (the generic term) in regard to making holes in them, but their are definitely a few rules you need to be aware of first.View Image
I-joist is a generic term for engineer wood based "i-beams".
Trust Joist or JTI is a trade mark for a specific brand.
Find the name stamp on them and then look up the manufacture and they will give you all of the specifics of installation and how/where/when you can put holes in them.
And look, some of them have marked knockouts that you can remove with a hammer.
Most people still call a circular bladed hand saw that you plug in a skilsaw, because they developed the market.
LKikewise. TJI held the original patent for wood I-beams. That patent expered about two years ago, so other manufacturers can now offer I-joists. The diff is brand name vs generic .
There are multiple configuations that satisfy differing structural requirements. For instance, the top and bottom chords can be of at least three different sizes, and the center flange can be phywood or osb and may be differing thicknesses.
Like DP, I was aghast at the thought of spanning the full distance until hearing the full story, but the supplier should be checking the engineering on the plans a he sells tham to you.
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Great, thanks!I'll try to get the numbers off the boards (something about being made in Canada) as to finding the manual for where I can drill the holes (just little 3/4" hole for the electrical wires).