18 foot lvl beam enough??

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  #1  
Old 01-22-10, 02:17 PM
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18 foot lvl beam enough??

I will try and put this as simple as I can.

I have a two story house with basement. It was built in 1980. The attic has trusses. The main floor consists of living room/kitchen/family room. Basically, I want to remove the wall between the kitchen and family room (it is 18 feet). The wall is load bearing. I know this wall is supported by the beam in the basement ( it runs the same path). And Above this wall is the master bedroom. The wall basically runs a path underneath the master bedroom at about the center of the room (so only the floor joist of the master bedroom rest on the wall).

I had a structural Engineer come out and evaluate. He said with an 19e Macrollam LVL beam you would probably have to go 3 ply 14 inches deep. I wanted to keep it 12 inches deep so he went back to his office did some cyphering and said 4 ply 12 inches deep would work.

My Question is what is the difference in strength between a 14 inch deep lvl and a 12 inch deep lvl ( in my 18 foot example ).
Give it to me in laymans terms.

My 4 ply 12 inch deep lvl beem in my example above is that more than enough??

Oh and the posts will be made of 4 - 2x8 at each end. The one end will rest on the concrete fondation. Both ends with blocking of course.

I just want to double check here, and when I go in to pay the engineer Monday I am going to go over it one more time.

 
  #2  
Old 01-22-10, 03:17 PM
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Probably, you will need a permit for this, and the Engineer's seal. For this reason and for your own safety (and your family's), I'd suggest to follow the engineer recomendations

An advice regarding a technical subject (something basic as the beam dimension and independent if you are paid for this advice or not) implies liability.
Ask or follow a structural advice provided through Internet is DANGEROUS
Structures / materials are quite different depending the characteristics of the project, load, soil / topography, wind conditions and seismic calculations.
 
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Old 01-22-10, 03:45 PM
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The reason the quad LVL was suggested was because you wanted a narrower profile. 3 ea 14" LVL's would work, but shorten the height to 12", you increase the flexion of the LVL over that span and have to boost it with an additional ply. We go through this quite a bit when head room is potentially sacrificed by tall LVL. We must go wide to compensate.
 
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Old 02-02-10, 11:44 AM
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Without seeing a x-section this is only a guess - and it can be a pain - but you may be able to put your new beam in "flush"/semi-flush - and hang the joists on each side. Depends on whether or not it would interfere with mechanical/electrical, etc.
Also, one end is going to bear on foundation. Other end? You're going to need to pick up 1/2 of the new point load on the other end. It is hard to consider every possible solution without knowing all the issues of the design. THere are two different loads to consider. THe "live" load and the "dead" load. If no one has done a cross section study of the situation, the engineer may be Over engineering. Also, is there room in your new floor plan to consider a bit more "partition" framing on one end or the other beneath your new beam line- thus decreasing the span of said beam.

Good Luck!

JH
 
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Old 02-02-10, 01:23 PM
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Hi NH,

The OP is talking about th main floor, not the basement
 
  #6  
Old 02-04-10, 09:59 AM
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Dear Citizenxca
Just "food for thought" as I like to say:
It is very likely that your home is held together by the paper on the drywall. Yes, one of the techniques we relied on back then to deal with SHEAR was to ensure that the drywall on the exterior walls was fastened in a paticular manner with the proper fasteners and it was imperitive that the paper not be torn through in the process. That said....

Once again, to address your desire to have your question answered in layman's terms, in the end - the final outcome is based on how springy a floor are you willing to live with?

The structural design community only cares a little as to how bouncy a floor you get out of the deal. Minimum design requirements often result in a less than desireable performance of the system.

Chandler handled the question well based on the consideration of flexion. However, You need to understand that there are multiple structural design constraints that must be considered. To that end, PMGCA was correct to stress the use of professionals and the irony created by comment back at me may be lost on many.

I touched on but only the simple design criteria as well. (Which was, after all your question.) But, you are not just transfering a floor load. That old and boring bearing wall dividing the existing rooms is dealing with SHEAR as well. (Even if nobody realized it when your House was built.)
Your new beam will not. So if this is "on the QT", please have your engineer consider the whole picture. All of the Engineered Lumber manufacturers publish load tables based on given minimum requirements. THe modern structural engineer must address snow, seismic and wind loads, of which tables exist for your region. Here is an excerpt of some design criteria from the folks at Weyerhaeuser..
■ Tables are based on:
– Uniform loads.
– More restrictive of simple or continuous span. Ratio of short span to long span should be greater than 0.4 to prevent uplift.
– Roof truss framing with 24" soffits.
– Exterior wall weights of 80 plf, interior 60 plf.
– Deflection criteria of L/360 live load and L/240 total load.
■ Tables do not consider attic loads acting concurrently with roof or snow loads.

For a further insight into LVL's, Paralams, etc.,
You can go to http://www.ilevel.com/literature/tj-9000.pdf

One more note: Engineered lumber is great. Just make sure to follow all the manufacturers guidelines as to Delivery, Job-site storage (keep 'em dry), as well as installation and the tragic aftermath that can occur with misinformed tradesman that follow the framer. Also, you may want to consider engineered lumber columns as well. They are expensive, but in the long run, as far as the finished product is concerned, well worth it.
Best Regards,

JH
 

Last edited by pmgca; 02-04-10 at 03:35 PM. Reason: Comment edited
  #7  
Old 02-09-10, 09:05 PM
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Thank you all for your information. This is a great forum with great people helping each other. I will heed all your recommendations. I have put up a 9 ft beam and I am now working on the 18 ft beam. Engineered approved of course.

Menoexpert _ extra thanks for the detail.

Wish me luck.


Citizenxca.
 
 

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