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Old 10-15-2008, 09:13 PM   #1
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Bridge spacing for 11 7/8 TGI's


Hopefully over the weekend ill be setting some joists which brings me to this question.

What would be a good spacing for a 22' run at 12 o.c. and a 17 1/2' run at 16 oc ?

The Bridge will be the cross type, not solid.

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Old 10-15-2008, 10:45 PM   #2
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Bridge spacing for 11 7/8 TGI's


22' is a long span! The more bridging you have, the better the floor will perform. Bridging allows the joists to share the imposed loads more effectively.

I'd use 6-8' apart as a general rule of thumb. Middle of the span for sure, but they'll benefit you anywhere you put them. If you're getting your joists from a reputable dealer, they should be able to provide engineering support for you and tell you what's ideal based on the joists' performance.

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Old 10-20-2008, 07:01 PM   #3
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Bridge spacing for 11 7/8 TGI's


no blocking/bridging is required for tgi joists. in fact your not allowed to nail into the top and bottom flanges along the span
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Old 10-20-2008, 08:45 PM   #4
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Bridge spacing for 11 7/8 TGI's


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no blocking/bridging is required for tgi joists. in fact your not allowed to nail into the top and bottom flanges along the span
Although none is required in most cases, it doesn't mean that the floor system won't benefit from it. And, you absolutely are allowed to nail into I-joists out in the span. Sheetrock, plywood, furdowns, non-load bearing walls, hangers, other joists, pipe hangers, and a number of other things are nailed into the joist flanges in the span. Most manufacturers limit the size of nail you can use in the flange to a 10d.

Simpson makes metal bridging that is a pretty good option...
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Old 10-20-2008, 09:44 PM   #5
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Bridge spacing for 11 7/8 TGI's


top and bottom yes but not into the sides of the flange
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Old 10-20-2008, 10:18 PM   #6
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Bridge spacing for 11 7/8 TGI's


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top and bottom yes but not into the sides of the flange
Can you link to some manufacturer literature outlining this requirement?
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Old 10-20-2008, 10:32 PM   #7
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Bridge spacing for 11 7/8 TGI's


not specifly. but the framers i know that use them say you cant nail into the sides of the flanges. if a hanger needs to be used for what ever reason you have to fill in the web and use a hanger that wraps on top of the joist.
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Old 10-20-2008, 11:02 PM   #8
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Bridge spacing for 11 7/8 TGI's


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Originally Posted by thekctermite View Post
Simpson makes metal bridging that is a pretty good option...
hey... thats what i used, think they where B20s for the 12oc and B27's for the 16oc.
For the 22 length i added three pairs to each bay and for the 17' used 2 pairs spaced in about 5-6' from the ends.

With out sheathing i could not beleave the difference it made. After doing the 12oc section i tossed up a few sheets a 3/4 T&G (just slid them on) just to make it eazyer to move around on the floor, the plywood was not too jiggly on the braced section, but when i slid the sheet over to the non-braced section, boy, it was almost scary (i do not like heights, the basment below was about 9' down of rebar and wire-mesh). In the end it worked great aside form all the nailing which had to be done by hand
Very glad the architect told me to use bridging and followed thekctermits tip.
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Old 10-21-2008, 07:59 PM   #9
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Bridge spacing for 11 7/8 TGI's


Moderator edit: Personal attacks not prohibited. TheKCtermite

@ OP - I would suggest you get a designer to check that span. Even a TJI360 doesn't really have a great deflection result for a span that long. You may need to go to 12" O.C. spacing
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Old 10-21-2008, 08:09 PM   #10
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Bridge spacing for 11 7/8 TGI's


hci blogger. "i dont know what im talking about" is that so. i work in houses every week doing decks and underlayment. my boss is a framer and i talk to the framers of the houses and they all say never nail into the sides of the flanges without filling in the web.
hci blogger are you a framer?
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Old 10-21-2008, 08:20 PM   #11
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Bridge spacing for 11 7/8 TGI's


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Originally Posted by iMisspell View Post
Hopefully over the weekend ill be setting some joists which brings me to this question.

What would be a good spacing for a 22' run at 12 o.c. and a 17 1/2' run at 16 oc ?

The Bridge will be the cross type, not solid.
You don't need bridging with I-joists unless you get a set of plans that call for it.
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Old 10-21-2008, 08:25 PM   #12
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Bridge spacing for 11 7/8 TGI's


I'm a structural engineer and I run a construction company....there is NO spec that calls for not nailing into the side of these joists.
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Old 10-21-2008, 08:33 PM   #13
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Bridge spacing for 11 7/8 TGI's


Quote:
Originally Posted by iMisspell View Post
hey... thats what i used, think they where B20s for the 12oc and B27's for the 16oc.
For the 22 length i added three pairs to each bay and for the 17' used 2 pairs spaced in about 5-6' from the ends.

With out sheathing i could not beleave the difference it made. After doing the 12oc section i tossed up a few sheets a 3/4 T&G (just slid them on) just to make it eazyer to move around on the floor, the plywood was not too jiggly on the braced section, but when i slid the sheet over to the non-braced section, boy, it was almost scary (i do not like heights, the basment below was about 9' down of rebar and wire-mesh). In the end it worked great aside form all the nailing which had to be done by hand
Very glad the architect told me to use bridging and followed thekctermits tip.
Glad it worked out for you. Thanks for letting us know how it worked.
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Old 10-21-2008, 11:59 PM   #14
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Bridge spacing for 11 7/8 TGI's


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Originally Posted by Joe Carola View Post
You don't need bridging with I-joists unless you get a set of plans that call for it.
The plans say, "as bridging per manuf", but i could not find info about it in thier pdf files and for got to ask at the lumber yard (i was probly to excited and over looked )

Quote:
Originally Posted by HCI Blogger View Post
@ OP - I would suggest you get a designer to check that span. Even a TJI360 doesn't really have a great deflection result for a span that long. You may need to go to 12" O.C. spacing
Thanks for your suggestion.

The architect said 23' with TJI 230's would be the limit and would have to be 12 o.c. and they could span 20' at 16 o.c. (a guy i work with did a 20' span at 16oc and said he does not notice any bounce, dont rember what kind of room he did, living/bed/etc.) The floor has a "knotch" in it for a stair-well, where that cut-out is, they span alittle over 17' at 16oc and for the 22' runs they are at 12oc.

All the sheathing is nailed except for the 22' run on the rim-board running parallel to the joists (was gonna do that today but it rained) and as far as me walking around theres no bounce, but i only weigh 175-180.

If problems or bounce apairs down the line, ill post back the results.


Last edited by iMisspell; 10-22-2008 at 12:04 AM.
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