2x6 over a 14' span

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Old 12-08-13, 07:58 PM
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2x6 over a 14' span

Working on a cottage that has 2x6 floor joists 24" OC supporting the second floor. The center of the house has a room that spans feet. The center of the room sags about 3/4".

I sistered 4 of the joists with lvl beams ripped down to match the 2x6's. It may have helped the deflection bit it didn't do anything for the sag.

Should I go through and add 2x6's between the lvls' s? The open bay is about 20". It would out the floor at about 10" OC.

Would it make a difference?
Is a lvl ripped to 2x6 (5 1/2) offer more support and less deflection than a 2x6?
 
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Old 12-11-13, 11:17 PM
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Building Codes provide a Guideline. You want to go above their guidelines.

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I am no Engineer but the Building codes for a 2x6 would not support a 14 Foot Span with No column support. Unless you have a Bearing Wall assiting the support.

Using TOP CHOICE Wood..a 2x6 would support a 12' 6" Span on 12" Center..But your normal Home Depot wood would only support 11' 6" with 12" on center. IF you have it 20" OC then the chart shows only a 9' span. and thats the Max. Should never be at the Max of a chart. reference the codes for the minimum link is below.

If you can get it above minimum then you will do better in the deflection. Sistering beams gives you extra strength such as support a tub. but if the span is too great it will still bounce and could eventually sag. LVL is pretty solid but you have to use the right size.

Chapter 5 - Floors


These codes are for NY in a Sleeping Room. But Most codes are similar . You may be able to find your own online.

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TABLE R502.3.1(1)FLOOR JOIST SPANS FOR COMMON LUMBER SPECIES (Residential sleeping areas, live load = 30 psf, L/∆ = 360)a
 
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Old 12-15-13, 04:18 PM
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Adding joists didn't help the sag because you didn't jack it up first.
 
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Old 12-15-13, 05:11 PM
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Not only that, ripping LVL didn't gain anything to speak of. LVL has its own span table. Not sure why you would have wasted good LVL. Could it not protrude above the 2 x 6's?
 
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Old 12-15-13, 06:45 PM
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I jacked up the 2x6's before I nailed the lvl to it. Maybe I should have jacked up just lvl???

I called the manufacturer of the lvl. They suggested two lvl's sistered together 12" oc. I don't know if it would level the floor but according to their charts it would span the 14 feet and would reduce deflection.

Also, the ceiling is only 7 .5' high. I can't really add a beam below it.

I can't reduce the span because the joists from the next room share the wall.
 
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Old 12-15-13, 07:10 PM
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I don't know if it would level the floor but according to their charts it would span the 14 feet and would reduce
Yeah, before you ripped them. You most likely don't need a beam. Sistering the joists would have entailed jacking up the joists and installing the full size LVL the length of the joists. Screwing and bolting the joists and LVL together
 
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Old 12-15-13, 07:25 PM
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Are the LVLs that you installed set on the top plates of each wall?
 
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Old 12-15-13, 08:51 PM
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No, he stated that two lvl's ripped to 5 1/2 and spaced at 12" oc could span 14 feet. Now, that is the guy who answered the phone. I have no idea what his background is.

Yes, the lvl's I installed run wall to wall and rest on the top plate on each end.
 
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Old 12-15-13, 10:00 PM
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I also should have asked which side of the LVLs you ripped. If you hold a long piece of wood on edge & look at it from one end to the other, you will see what's called the crown. In other words, there will be a slight curve upwards. If you flip it the other way, the curve will go the other way, as well. That curve should face upwards when it's installed. You ripped the LVLs possibly removing the crown. That could have made the difference with the sag.
 
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Old 12-16-13, 06:08 AM
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Ugh, I wasnt aware that they had a crown. If the crown is up it would be out of luck.
Odd that the lumber yard had no problem ripping it. In fact, it may have been their idea.

Although I was able to put one end over the top plate on one side and I was still able to lift the the beam high enough to clear the top plare of the opposite wall. It was only off by less than an inch but it flexed fairly easy. I don't think it would be strong enough to remove the sag without adding a second lvl.
 
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Old 12-16-13, 06:19 AM
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The idea is that the LVL doesn't lift the floor. You lift it before you install the LVL. The LVL just keeps it there. So, if the sag wasn't corrected first, everything remained the same. At the same time, it won't get any worse.
 
 

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