Acceptable TJI Squash Blocking

jerkyboy

I'm working with a framer on a job and we are using a TJI system. I am an electrician by trade but I'm helping frame. I helped frame a TJI addition a few months ago and we used 2x4s for squash blocks but the framer on this job insists that we use pieces of scrap TJIs as squash blocks; says he's done it hundreds of times and it doesn't sacrifice structural integrity. Any thoughts??

KentWhitten

I guess if he insists, and it's his job, and he's paying the wages, then it gets done that way. There are reference materials about this and I don't remember seeing scrap TJI's used as squash blocks. I do remember seeing 2x4's. He's not talking about using them vertically is he? Like ripping off the ply web and using the bottom chord like a stud?

If that's the case, it should be completely fine. If he's using it like blocking, don't think that will actually qualify as squash blocking because it's relying on the web for squashing.

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RobertCDF

I this point loading? Or are you maybe thinking of ROLL blocks? I cant see using TJI as point load blocks. Only thing to use TJI for is roll blocking.

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jerkyboy

No, he is not using the bottom chord for squash. He's using anothter 9 1/2" TJI on both sides. I read through the literature and it shows a vertical 2x 1/16" taller than the TJI to take the load. I have a vested interest in this job, so I want to make sure it's done correctly.

wallmaxx

Every time I've used I-Joists, they were engineered for the job. The floor system engineering supersedes the architectural requirements or structural engineering noted in the prints and becomes the law for the floor system. I always installed the floor system as directed by the literature provided by the guys who delivered the joists. i.e. LP has a list of authorized installation methods that they accept when assembling their joists in a floor system. You already know the right answer. Here is the image from the LP site.


I haven't seen them say NOT to use pieces of I-Joist, but if it was me I would approach your com padre and come from the angle that you were reading up on this stuff, and that you wanted to make sure that "we" wouldn't get in any trouble for not installing the joists as prescribed by the manufacturer. Something little like this can come back to bite you. It would suck to have the floor system fail inspection, and then you'd be putting in 2x4 blocks with the decking in your way.

Good luck to you.

Mike

shed-n-deck

In Colorado, we call them "Point Loads". I've used TJ's and 2x's for sqaush blocks...With TJ's, a single is usually sufficient, as long as full bearing is obtained, with 2x's, you have to match what is loading down on the squash blocks and place them directly under the load. More typically, I've used the same material as the rim joists...Usually it's LSL....As long as full bearing is obtained, I've never had a problem...

I should say this: It's been 6 years since I've framed a house, so things may have changed quite a bit. Don't depend on my advice, ever...To be sure, use 2x4's(or whatever you use to frame your walls).

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Kingfisher

Never have used them. Do I understand right they can't support the wall load? Why not just use truss or real wood, are they that much cheaper?

dlcj

I-joist are more expensive than lumber of the same hight here but they are alot stronger and lighter. They can span alot farther resulting in less overal framing for a faster, stronger, and flater floor at a comparible price. We have used some as long as 48' and 2 men can frame a floor system as fast as 4 men using 2x10s. The load blocking is needed where the joist cross a beam and a load bearing wall is above. The 3/8" osb will crush at that point if not reinforced.

RobertCDF

All our studs always stacked on the BCI joists. And any sort of post had solid blocking from the post, or trimmer/king studs down to the foundation or midspan beam.

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Colorado Springs Custom Decks
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framergreg

i have framed with i joists for years in both resi and comm jobs. wallmax has it right , u must use 2xblocking for all bearing/loadpoints with filler blocks(plywood)on bothsides of joist to form solid sandwhich. anylumberyard can give you a framing detail sheet from the product maker u are using. inspectors here in Mn love to nail those who use chipboard as a block.....its not gonna pass the test.

Kgmz

The big question is what does the engineered design say?

Not the typical detail sheet that comes with the TJI's that shows all situations.


Are the TJI blocks being install parallel or perpendicular to the run?


Also what code is used where you are at? IRC, UBC, etc.?

We changed to the IRC a couple of years ago and there were big changes with TJI's. We hardly ever use squash blocks now because there now has to be solid TJI blocking over all supporting walls and beams whether there is a load above or not. The reason for this is to give extra support for loads above and for roll stiffness.

Higgs

out of question what is the purpose of squash blocking is it just for supporting the load from the well above the joist?

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KentWhitten

Squash blocking is for support of a point load coming from a post above. A door or window really is considered a post or a point load. The load gets transferred through the bottom plate, through the subfloor, then when it hits the level of floor framing, there needs to be something there to transfer the load to the sill plate then to the foundation.

In TJI systems, you have this squash block that transfers this load. I hav ebeen under the impression for years, that the block is a 2x, vertical, that is cut 1/16" longer than the thickness of the joist in question, to accept this load rather than the end of the TJI's being just a 3/8" OSB core (usually)

In some instances, all the ends of the TJI's resting on the bearing wall will be required to have squash blocking, but it depends on the overall load. Usually, you sister something to the sides of the TJI web in order to accomplish this.

WA state was my experience with inspectors getting on your case about these. You HAD to have them in for you to continue. Don't put them in, you go nowhere. They were prickly about it.

Being scrap pieces, I'd seriously doubt they would be considered good for this. You would only have (2) 3/8" pieces of OSB instead of one.

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Custom Cabinetry - Portland, Cape Elizabeth, Scarborough, Kennebunkport, Yarmouth, Falmouth, Cumberland, Ogunquit, Maine

Salmon Falls Cabinetry

neolitic

Have only used these in simple additions for clear span below, so no bearing walls. Doesn't that detail suck big time for mechanicals running from floor to floor? Looks like that would make wall stacks and R/A's a bear?

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JustaFramer

Another reason I hate rolling TJI's. Yeah they are easy but the work that goes into getting them structrual is rediculous especially on a 2000 sq ft. subfloors with multiple loads from the upper floors.

tinner666

Thanks for this thread. I hadn't used them before, but I sure learned something new here.

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clampman

Kgmz,

You said it all with "Do what the engineering details show". As long ago as 1979 in Vail, we had to use coped TJI's between joists everywhere for roll blocking and solid blocking in addition for point loads. Point loads were spec'd on the print details. I don't remember about the roll blocking - just that we had to do it.
I probably should add "....engiineering details AND the local inspectors"

clampman

double post

72chevy4x4

the LP book I looked at shows systems w/ squash blocks and w/o-seems to depend on the load. Around my parts, engineered lumber requires an engineer, which the local lumber house sends the plans to the company's engineer (LP in this case), who will note the required blocking. If an engineer noted blocking as he is using, then it should be deemed ok-if no engineer signed off on the system, I would go w/ 2x blocking to be on the safe side (i.e. overbuild it).

Pavola

I agree with chevy. Each floor system is engineered for the house design so all the requirements should be noted on the layout plan.