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TJI rim joists

Jay345's picture

I'm thinking that it would be structuraly more sound to use a 1x10 rim joist with TJI floor systems rather than that 1" flake board that is usualy sent with the package. This would make it a lot easier to attach decks, porches, ect. Does any one see a problem with that?

(post #100257, reply #1 of 9)

I've never seen a 1x rim joist. I wouldn't think that any 1x material would be sufficient for supporting a ledger.

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(post #100257, reply #2 of 9)

"I'm thinking that it would be structurally more sound to use a 1x10 rim joist with TJI floor systems rather than that 1" flake board that is usually sent with the package. This would make it a lot easier to attach decks, porches, ect. Does any one see a problem with that?"

Yes. A 1x10 rimboard is not in any Instructions for I-joists that I've ever seen before. Also a 1x10 is only 3/4". The rimboard ususally measure 1-3/16" from where I'm from anyway.

You can't change the way you frame with I-joists. You have to FOLLOW the manufactures Instructions for I-joists unless you get something in writing from an Architect or Engineer, Period!

The only thing that I have done and was approved by Architects is used a 1-3/4" microlam for the rimboard and then bolted the deck ledger to that. You can't do that if the rimboard is perpendicular to the I-joists because the I-joists will not have full bearing if you have a 2x4 wall as far as I know.

They say that the rimboard is structurally strong enough for deck ledgers.

Joe Carola

Edited 1/22/2006 9:43 am ET by Framer

Joe Carola

(post #100257, reply #3 of 9)


For the last four years I have used 1-3/4" LVL (microlam) stock for rims because I'm not comfortable with the 1-3/16" LSL rimboard stock under pressure. TJI's have a tendency to compress under weight (hence the solid blocking recommended by the manufacturer under bearing walls) and to avoid the crush factor, LVL's fit the situation. I know its overkill, but I would rather be safe than sorry, especially on larger frames with crazy point loads.

Although my perspective on LSL stock may change with the new TJI engineered roof framing system available. I hope to use it on my current project. Different thickness than the rimboard though.


The CM


Edited 1/22/2006 1:47 pm ET by the cm


The CM


(post #100257, reply #4 of 9)

Most rim board that I know of is rated for something like 2,000 PLF.

The 1X lumber that you mentioned doesn't match the depth of the I-joists and isn't approved by the manufacturers. And I doubt is has nearly the load capacity that rim board does.

I doubt any building instector would go for it without engineering backing.

So I think you'd be foolish to use it.

Why isn't there mouse-flavored cat food?

(post #100257, reply #8 of 9)


Mouse flavored cat food. LOL. Where do you find this great stuff? (not the cat food).


The CM


Edited 1/22/2006 1:59 pm ET by the cm


The CM


(post #100257, reply #9 of 9)

Here's a post where I explained my tag lines:

Zsa Zsa Gabor, when asked which of the Gabor women was the oldest, said:
"She'll never admit it, but I believe it is mama."

(post #100257, reply #5 of 9)

No way would I use a 1x10 board where structural lumber is needed.

We use an engineered product that is 1-1/4" thick. The yard tells me that it is made for rim board with TJIs. Can't recall the name of it right now. Timberstrand rings a bell, but i can't swear to it.

I don't like mixing a 2x10 rim either, cuasse it will shrink more than the TJI will, increasing the loading on the TJI to where squash blocks would be needed.



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(post #100257, reply #6 of 9)

TrusJoist makes their rimboard stock in LSL, laminated strand lumber, and calls it Timberstrand.

Boise, Jager, and other I-joist makers ship a thick OSB product for use as rims.

Sawn lumber rims would be a poor choice if mixing with an I-joist frame, mainly because of the large shrinkage differential between the sawn stock and the engineered product.

If there is a concern about the lack of sufficient purchase for deck ledger lagscrews, I would back up the rim with blocking in those areas.

(post #100257, reply #7 of 9)

As others have noted, a solid lumber rim is not an option for TJI joists (In time, it will shrink away from the top of joist line and your subfloor and bottom plate will, in effect, be cantilevered.  In addition, the TJI warranty will be compromised.

I usually use "Versa Rim" with engineered joists;  most available to me are BCI's (Boise Cascade) and I believe Versa Rim is their product (an LVL), 1 1/16" thick.  Where I've got a deck or a concern about bearing, I just step up to a thicker LVL, usually 1 3/4" lets me sleep.

BTW, your joist package should come with the manufacturer's instruction sheet.  These instructions are pretty specific about rim joists, blocking, squash blocks, cantilever reinforcement, headers, etc.  If you haven't used engineered lumber before, you need to acquaint yourself to their use.....bear in mind that they're a construction system and, in most cases, are not meant to be comingled with non engineered materials.

And really begin to appreciate that, while they have their virtues, some of us here who have to install them, are not particularly enamored with them.


Edited 1/22/2006 1:27 pm by Notchman