TJI Issue

[XR250]

Looked at a house today with 20' span, 11 7/8" TJI230 spaced 19.2" O.C. In an open room with vinyl plank flooring, the joists were sagging 1/2".
I looked at an old TJI table and they are rated at 19'-11 at this depth and span for L/360. So basically meet minimum code - Yay!
In a current TJI catalog, they are only rated for 17'-9" (vibration controlled).
The house is 4 years old. Does anyone know when TJI changed their recommendations from span/deflection to vibration?
There was also a footnote in the older catalog about long-term creep not being considered (apparently not!)

1) This is why I f'n despise I-joists.
2) This is why i f'n despise production builders

The house supposedly has a 10 year structural warranty. I imagine they will do their best not to help this homeowner.

 

[phamENG]

Homeowner is likely up a creek on this on. New catalog actually says this one is good for 20'5" at code minimum.

Unless the contractor committed to providing something excess of the code (which I doubt), they had not obligation to go by the L/480 recommendation anyway.

 

[XR250]

Where are you getting that table? When I go to their website, I only get the one with vibration controlled tables.

 

[jhnblgr]

SPECIFIER'S GUIDE FOR TJI 110, 210, 230, 360, AND 560 JOISTS - USA - tj-4000

Featuring Trus Joist® TJI® Joists for Floor and Roof Applications

www.weyerhaeuser.com

 

[XR250]

Thanks

 

[TRAK.Structural]

I don't like wooden I-joists either because they always end up with holes and notches that need fixing. I've found that BCI spans are generally better so I have started calling for those.

 

[RontheRedneck]

I don't have a problem with I-joists in general. But I strongly recommend that the span to depth ratio is no more than 18 to 1. i.e. an 11 7/8" I-joist should span no more than 18', no matter what the flange width.

It was somewhere in the 1990s that I-joist manufacturers started moving away from the L/360 deflection criteria and went to L/480. That was when research on floor vibration became widely available. We did the same with floor trusses.

Contractors and framers for some reason seem determined to only use the 11 7/8" depth, and they want to push the spans as far as they can. I push back. But I have no authority to make them do anything.

But I've influenced things enough locally that we rarely get complaints about floor vibration.


In the case in the OP, I believe 1/2" of deflection is still less than L/480. (Don't have a calculator handy) But it's a longer span to depth ratio than I would recommend now.

Back when that house was built - Who knows. I've learned a lot since then. Others have too.

 

[GaStruct]

I don’t really have any answers to your question @XR250 except that I never use span tables for I joists design for this reason (I know you didn’t design it here). For TJI design I use forte. They integrate their “pro rating” which I like for serviceability concerns that include deflection and vibration.

I too hate production builders, BUT, I actually like I joists. They are dead nuts level which is tough with 2x at longer spans. Plus you can cut out big holes in them for MEP. And they can span over 24’ no problem. Tough to beat!

I know you’re a 2x man tho. I always over design my I joists to mitigate issues.

 

[XR250]

Back when that house was built - Who knows. I've learned a lot since then. Others have too.

I mean its only 4 years old. First I have seen of an L/360 I-joist floor in years.

 

[Eng16080]

I'm not defending I-joists here, but 1/2" deflection doesn't seem that bad. I suppose it's probably not supporting anything near the design load though. How heavy is the flooring?

Last time I had an I-joist spanning 20 ft at only 11 7/8" deep, I think I used the 560 product.

 

[RontheRedneck]

I mean its only 4 years old. First I have seen of an L/360 I-joist floor in years.

Sorry - I missed that in the OP.

I'm guessing it's what I said "Contractors and framers for some reason seem determined to only use the 11 7/8" depth, and they want to push the spans as far as they can." I find that both puzzling and annoying.

 

[XR250]

I'm not defending I-joists here, but 1/2" deflection doesn't seem that bad. I suppose it's probably not supporting anything near the design load though. How heavy is the flooring?

Last time I had an I-joist spanning 20 ft at only 11 7/8" deep, I think I used the 560 product.

It's just LVP flooring. 1/2" is way too much IMHO. Enough that it is noticeable and the homeowner does not like it.

 

[jerseyshore]

I love TJIs but never look at the tables. I'd be curious to see how this setup fares in forte for deflection and TJ pro rating. I don't think I've ever seen 19.2" o/c joists in my life so that screams super cheap to me.

This is why residential designs are always L/480 for me because even the smallest issues get lots of complaints.

 

[XR250]

I usually see 24" O.C. in tract homes. I feel like 19.2" O.C. is the builder "trying" to do the right thing.
Even L/480 can feel bouncy on longer open spans. I try for L/600 or better when possible. Even tighter in kitchens where long-term creep becomes a factor.

 

[jerseyshore]

I usually see 24" O.C. in tract homes. I feel like 19.2" O.C. is the builder "trying" to do the right thing.
Even L/480 can feel bouncy on longer open spans. I try for L/600 or better when possible. Even tighter in kitchens where long-term creep becomes a factor.

Don't think I've seen an I Joist at 24" o/c either. That's for open web trusses or pre 1940s houses.

Yeah I'm a L/480 minimum type person with heavier loads and/or tighter deflection criteria in kitchens and decks.