Engineered I Beams

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  #1  
Old 01-27-08, 11:49 AM
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Engineered I Beams

I'm wanting to span a 31 foot opening in a living room of the house I'm going to build. Can I use 2x12x31' engineered I beams
for this without any support below?
 
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  #2  
Old 01-27-08, 01:06 PM
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Off the top of my head, i can tell you 12" deep i joists wont make that span. You'll have to go 14" or 16" deep. But even the highest grade 14" on 12" centers will likely result in bouncy floors. I wouldnt be suprised if you have to do 2x16's on 12" centers to achieve the desired effect.

check these tables:
http://www.naffainc.com/x/cb2/tables...oistsTable.htm
 
  #3  
Old 01-27-08, 03:54 PM
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I beams

I trying to decide if I want to go through the added cost to build for future expansion. It looks like it's going to be more trouble and expense then I want. If the 31' expanse isn't to be used for a second floor but maybe some storage What I could get by with? I not sure I'm reading the chart right that you sent.
Thanks

Originally Posted by OhioDraft View Post
Off the top of my head, i can tell you 12" deep i joists wont make that span. You'll have to go 14" or 16" deep. But even the highest grade 14" on 12" centers will likely result in bouncy floors. I wouldnt be suprised if you have to do 2x16's on 12" centers to achieve the desired effect.

check these tables:
http://www.naffainc.com/x/cb2/tables...oistsTable.htm
 

Last edited by JBURD964; 01-27-08 at 03:55 PM. Reason: spelling
  #4  
Old 01-27-08, 06:19 PM
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well if you intend to use it for storage, springy floors are not your concern. It looks like you can get away with 2x14's on 12" centers. Also, i am not sure if those tables i gave you the link to are completely current, i just did a quick google and found those. Here is a page that has the current span tables for TJI joists, scroll down to the 4th page of the pdf file: http://www.ilevel.com/literature/TJ-4000.pdf
You'll have to check with your local building officials to see exactly what deflection criteria they expect out of liveable vs. non-liveable spaces to see if you maybe downsize those a bit. But i am pretty sure you'll need to use the TJI 2x14" 560 series joists spaced on 12" centers.
 
  #5  
Old 01-27-08, 06:52 PM
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Engineered I Beams

There is a difference between strength, deflection and "springiness".

Tables will usually give what is enough to carry the load. Often there are more important things if you expect to live in the house and have it look good.

Excessive deflection can cause cracks and deflection. One common rule of thumb is 1/360. For a 30' span (360 inches), a 1" deflection is allowable under that guide.

For springiness, this is psychological and different people have a different sense of what is acceptable. - I had a college professor (structural engineer) that would not buy a home with a wood floor system since he was raised where they only had concrete floors in 2 story homes. He knew the house was strong enough, but did not like the flimsy feel of "vood".

There are more important things than code minimums.
 
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Old 01-28-08, 05:25 PM
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Thanks Again..........
Originally Posted by OhioDraft View Post
well if you intend to use it for storage, springy floors are not your concern. It looks like you can get away with 2x14's on 12" centers. Also, i am not sure if those tables i gave you the link to are completely current, i just did a quick google and found those. Here is a page that has the current span tables for TJI joists, scroll down to the 4th page of the pdf file: http://www.ilevel.com/literature/TJ-4000.pdf
You'll have to check with your local building officials to see exactly what deflection criteria they expect out of liveable vs. non-liveable spaces to see if you maybe downsize those a bit. But i am pretty sure you'll need to use the TJI 2x14" 560 series joists spaced on 12" centers.
 
  #7  
Old 01-28-08, 06:12 PM
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Thanks for your perspective. Hadn't considered anything other then expense.



Originally Posted by Concretemasonry View Post
There is a difference between strength, deflection and "springiness".

Tables will usually give what is enough to carry the load. Often there are more important things if you expect to live in the house and have it look good.

Excessive deflection can cause cracks and deflection. One common rule of thumb is 1/360. For a 30' span (360 inches), a 1" deflection is allowable under that guide.

For springiness, this is psychological and different people have a different sense of what is acceptable. - I had a college professor (structural engineer) that would not buy a home with a wood floor system since he was raised where they only had concrete floors in 2 story homes. He knew the house was strong enough, but did not like the flimsy feel of "vood".

There are more important things than code minimums.
 
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