Floor Trusses

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Old 03-26-2008, 11:45 PM   #1
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Floor Trusses

I have never worked with Floor Trusses before. We are building a small cabin (24 X 24) with a full basement for a guy. He doesn't want any walls or posts in the basement. Can I use Floor trusses and what size will I need. They will be 16oc. Thanks for the help.

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Old 03-26-2008, 11:56 PM   #2
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Re: Floor Trusses

I'm planing a shop soon and will use the same joists as well. You can get all the specs (span tables, joist height, centers...) for engineered joists off the internet for your application.


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Old 03-27-2008, 12:09 AM   #3
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Re: Floor Trusses

It will depend on your manufacturer.

I have seen some companies 12" trusses that will span the 24' you need, while others will require a 14" or 16" truss at the 16" O.C. you specified.

Also most companies will have a maximum span of 30' regardless of the O.C. spacing, but my local truss manufacturer has just announced that they can build floor trusses that will span up to 34' now.

So your best bet is to talk to whom ever will manufacture then for you.

Also you can use Weyerhauser 12" 560 TJI's or Boise Cascade 90 2.0 TJI's at 16" O.C.

Last edited by Kgmz; 03-27-2008 at 12:19 AM.
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Old 03-27-2008, 02:32 AM   #4
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Re: Floor Trusses

The truss manufacturer provides the engineering needed to permit the project. Take a set of plans into the manufacturer and he will be able to tell you what depth truss is needed to make the longest span, then engineer all trusses to that depth.
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Old 03-27-2008, 05:21 AM   #5
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Re: Floor Trusses

Originally Posted by supermike View Post
I'm planing a shop soon and will use the same joists as well. You can get all the specs (span tables, joist height, centers...) for engineered joists off the internet for your application.
He's talking about floor trusses not engineered lumber. Even if he was, you have no idea what this guy is building, nor any of his loads, nor the local codes of where he is building. This is easily done by the QUALIFIED truss engineer. He will answer all your questions and design your floor accordingly.
If you correct your mind, the rest of your life will fall into place ~Lao Tzu


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Old 03-27-2008, 07:10 AM   #6
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Re: Floor Trusses

i would span a header across the middle to carry the load , hide the studs in the walls if you can youll only be loosing a lil bit of head space .use 2x12 , or lam beams for header , 2x8 for the floor trusses in fir , not using any supports could cause problems down the road , doors windows ect . will also take out any bounce in the floors ,pretty sure most codes will want some kind of support there 16"o.c should be fine

Last edited by odellconstruct; 03-27-2008 at 07:15 AM.
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Old 04-06-2008, 09:18 AM   #7
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Re: Floor Trusses

I'll second what KGMZ said. A 16" floor truss would have no problems with this span. And you might be able to go a little smaller yet. I'm not sure why you say 16" O.C. when you haven't even got your joists figured. If it ended up being a bit of a stretch (Which I'm sure it won't be in this situation), you could always drop to 12" O.C.to stiffen things up. While TJI's will certainly work, too, if he doesn't want any walls or posts/beams in the basement, he will certainly appreciate being able to run all his mechanicals throught the floor trusses instead of under TJI's.

I'd talk to my lumber salesman and my truss supplier in this situation. They will be able to figure the specs for this and set you right up.

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Old 04-06-2008, 02:52 PM   #8
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Re: Floor Trusses

Just be careful of the trampoline (the bounce factor) effect.

With long span (24' is not that long) wood or steel trusses, stiffness is an equal factor to strength.

Your supplier should take that into consideration.
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Old 04-08-2008, 07:12 PM   #9
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Re: Floor Trusses

At that span I'd be sure and have the truss company design for L/480 deflection, or you will end up feeling to much bounce. Even using L/480 deflection you would be allowed 6/10 inch bounce. I'd also put in some extra strongbacks to stiffen it some more. My own home has 26 foot spans and to much bounce as far as I'm concerned.

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Old 04-09-2008, 07:29 PM   #10
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Re: Floor Trusses

you can use a open web trus 16 inch as long as you dont have any load on you inside walls.


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