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Old 02-17-2010, 01:25 PM   #1
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LVL sag

I have 3 LVL across a living room on a two story house. The house is 15 yrs old. Construction co no longer in business. The LVL's span 21 feet and have the second floor joist saddle in joice hangers on both sides. Over the 15 yr period, these LVL's have sagged in the middle by approx 1 1/4" causing doors on the secound floor to go out of alignment. Also some drywall cracking. My question is, is it possible to jack these back up and hold them with a 1/2 by 18" steel plate bolted to one side and a new LVL also bolted on the out side of the steel plate to carry the floor joist. The LVL measure 1 3/4 thick and 18" wide. As stated there are three of them sandwiched together. The steel plate is 21' by 18" by 1/2" thick and weighs 660 lbs. Getting the plate in place is not a problem. Just wondering if the original LVL's will bend back to staight when we start jacking up the middle. We will be using three 12 ton jacks spread out on the center of the LVL
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Old 02-17-2010, 02:04 PM   #2
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Having 3, 18" thick LVL's sag like that would make me think there's an enormous load on them to deflect 1 1/4". Have you spoke to a professional about this? You can add this and that, but considering what was put there initially isn't doing the job, I'd get onsite advice and not guess at a solution.
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Old 02-17-2010, 02:11 PM   #3
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Who installed these ?
Was an engineer involved & sign off on the plans ?
If so they are on the hook for repairs if it was installed per their specs
If not hire an engineer to calc the load & prepare a plan to fix this
Jacking this up without a plan could cause the floor/support below to fail

No-one can size this for your over the Internet

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Old 02-17-2010, 03:22 PM   #4
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Your post was difficult to follow. Based on my interpretation, you have a triple LVL main beam that is sagging more than you like, and you are considering installation of a steel plate to increase the strength of the element. A combined wood/steel beam such as you appear to be considering is known as a flitch beam. Design of such a beam generally requires analysis by a competent engineer, and must consider structural issues such as bending, shear, buckling, and connection details. Installation is another complex consideration, given that the beam you describe is more than 600 lbs. You definitely need professional assistance from an on site structural engineer. Design and analysis of a flitch beam is way beyond DIY.
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