What's the difference between a floor joist and a beam?


dshall
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.....  the answer my friends is blowing in the wind.....  a beam can be a BEARING BEAM whereas a floor joist cannot.   Why is that?  I suppose it is not a big deal,  but why not. If I want to define a floor joist as bearing why can't I?  Is there a downside?

 

Are there anymore differences on the behaviors between the two?

 

Another difference would be the layer they would go on,  but again why can't a joist be bearing>

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I got curious enough to do a google for a construction dictionary

the first one I looked at matched my understanding of the difference (limited)

 

http://www.dictionaryofconstruction.com/definition/joist.html

 

http://www.dictionaryofconstruction.com/definition/beam.html

 

I was assuming a "joist" was a  2x? - seems they can be thicker

key seems to be that they are support for floors or ceiling

 

key for beam is transferring load to a vertical member

 

http://www.dictionaryofconstruction.com/definition/rim-joist.html

 

 

rafters for a roof would seem to be the same as "joists" for floors and ceilings - 2x?

yet the industry gave them a different name

http://www.dictionaryofconstruction.com/definition/rafter.html

 

I'm sure most on this forum already know this - but I got curious

and I'm sure newbies will read this thread in the future

 

 

Lew

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joist   [joist]  Show IPA


noun
1.
any of a number of small, parallel beams of timber, steel,reinforced concrete, etc., for supporting floors, ceilings, or the like.





 


See,  a joist by definition is a beam,  but a series of beams.  So why can't we define them as being BEARING.

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From the CA online help for beams:

 

Check Bearing Beam to specify the selected Floor/Ceiling Beam as a load-bearing beam. When checked, automatically generated joists run perpendicular to the selected beam and either lap or butt over it, as specified in the Build Framing dialog. SeeFloor Panels. Only available for Floor/Ceiling Beams.

 

The default settings for beams and joists seem to be "optimized" for the intended use.

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  • 1 year later...

 

 

Quote

 

See,  a joist by definition is a beam,  but a series of beams.  So why can't we define them as being BEARING.

 

Are You Serious!

Really!

Are we over thinking here? Do you have nothing better to do? I mean, what brought all this up? is there a valid point that you are trying to make?

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Are You Serious!

Really!

Are we over thinking here? Do you have nothing better to do? I mean, what brought all this up? is there a valid point that you are trying to make?

I know, sounds dumb now. There is or was a point. I assume you know that joists break over a bearing beam, and are continuous over non bearing beam, so I am assuming I ran into a situation where I wanted that option for a floor joist. But I cannot think of an example now.

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I know, sounds dumb now. There is or was a point. I assume you know that joists break over a bearing beam, and are continuous over non bearing beam, so I am assuming I ran into a situation where I wanted that option for a floor joist. But I cannot think of an example now.

 

I was assuming when you first posted that maybe you were coming up with some genius technique to do something with joist to help manipulate the framing for better use for beams or something. But then it sort of went know where. My expectations of your work is very high so I felt a little let down :(

But your still one of my hero's in the forum :D

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.....  the answer my friends is blowing in the wind.....  a beam can be a BEARING BEAM whereas a floor joist cannot.   Why is that?  I suppose it is not a big deal,  but why not. If I want to define a floor joist as bearing why can't I?  Is there a downside?

 

Are there anymore differences on the behaviors between the two?

 

Another difference would be the layer they would go on,  but again why can't a joist be bearing>

 

I'm sure you have a much deeper reason for asking than what it appears on the surface...at least I hope you do.  Joe put it best when he said..."Because its a joist..."

 

Its simply one of the many terms we use for communication purposes.  A joist by definition does what a joist does and a beam does what a beam does.  A 2x10 can be used as a beam, and a 4x12 can be used as a joist.  It all depends on the situation.  By calling it a beam (or a joist) you are stating what its purpose is.  Its kinda like asking what the difference between a stud and a post is, or even what the difference between a slab and a footer is.  Sure you can use a stud or group of studs as a post but a stud is not a post, and you could build a walkway with a 36" wide x 16" deep slab filled with rebar but that doesn't make it a footer. 

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You can also break any floor joists anywhere you want to by just drawing a bearing line anywhere on the plan.

 

Perry,

 

Are you saying this is possible after the joist have been drawn? I am not getting that result if your answer is yes. Can you elaborate?

 

Thanks

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Perry,

 

Are you saying this is possible after the joist have been drawn? I am not getting that result if your answer is yes. Can you elaborate?

 

Thanks

Yes but make sure you have auto rebuild floors/ ceiling on.

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