I beam required free span 18'

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  #1  
Old 03-07-04, 11:56 AM
Jackofall
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I beam required free span 18'

I need to support a bedroom which has a sagging floor. It has #2 pine 2x10 16 oc spanning 16'. The room is 18' x 16' so Id like to install a steel I beam to support the 16' 2" x 10"s. The I beam will be 18' free span.

What size I beam will support this sagging floor with no additional supports in the center so the existing floor will be level again? Does the steel beam need to be prestressed (bent a bit)so that it is level after installed? I cant find any span tables for steel I beams.

Thanks
 
  #2  
Old 03-07-04, 09:29 PM
bungalow jeff
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There are span calculators on line, but you are missing information. Where is this beam going (under the existing framing, or in the same vertical space for headroom considerations)? Steel beams require steel posts by code, and these posts will require proper footings.

Have you considered engineered timber for this application? Steel is not economical in this light span/load application. Usually the engineered lumber supplier can engineer the beam size, however a structural engineer may be required anyway by your local building official. An engineer can figure out the best solution for your specific situation.
 
  #3  
Old 03-08-04, 07:58 PM
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You can use 3 2x12 glue Lam beams side by side and fastened together. Not a problem. Alot cheaper then steel, easier to work with. You will need a 6x6 post at each end. You will have to put the Lam beams in place the then jack them up until your floor is level, then cut your posts to fit. Not a good job, unless you have done this type of work before. We are doing one now, with a 22' span. 5 guys. One mistake or slip and you will have big problems real quick. Good Luck
 
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Old 03-09-04, 03:53 PM
Jackofall
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Thanks.

The beam will be under the exisiting joists & I hoped a 10" tall steel I beam would carry the load. (less than $200) I guess the 12" joists would not be to much lower & cheaper. Its a basement shop below with concrete walls. Can I bolt a piece of angle Iron onto the concrete to support the beam? Or drill out a notch or pocket for the beam to sit in?

Thanks
 
  #5  
Old 03-09-04, 05:38 PM
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If you are going to use the steel beam, you must also use steel beam posts the same width as the web of your beam. These steel posts bust also have a concrete footing under them. Usually a 12" x 12" by 18" deep with rebar.
 
  #6  
Old 03-16-04, 05:42 AM
S
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Steel gets very heavy, very fast. Pound per pound, wood is twice as strong as steel. If you work with multiple beams as Jack says, you could bring the LVL beams to the site one at a time.

Unless the steel comes with crew as part of the price I would tend to look at materials/techniques that don't demand a half-dozen helpers.

I recently sorted through a stack of pressure-treated 2x12x16 footers. Loaded three on my car-top and unloaded them at home. I doubt I could do that with structural steel.
 
  #7  
Old 03-17-04, 07:04 AM
glimbaugh
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just think

what will happen if your steal beam is too long when you get it to the site. How will you cut it? If you go with wood you can cut it if too long.

One thing that you must verify before taking the sizing suggestion of jack. Make sure that the loads above this room aren't being transfered back to this beam.

For example:
there could be a roof truss bearing on a wall which sits on top of this beam. If this is the case the 3 PLY LVL might not be strong enough. If it is just the floor area that you describe then it should be fine.

Also: Your beam should be secured with a hanger specifically made for this type of situation. Simpson strongtie makes a hanger for this the model is called WM(Welded Masonary)then specify H x W this hanger and carries about 4100 lbs. Your application will require a hanger capable of supporting 3600 lbs.
 
 

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