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I am framing a home and used built up micro-lam beams for the major cross beams. For the longest span the beam consists of four 1-3/4″ x 12″ micro-lams bolted together. I noticed (while trying to track down some floor squeaks) that the outside boards have sagged (I have joists attached to both outside beams). My conclusion is that I didn’t put enough carriage bolts through to transfer bearing through to all 4 beams. I came up with two solutions 1) jack-up the two outside beams and then add carriage bolts to carry the weight through or 2) just add carriage bolts to prevent any further deflection.
My question is, I guess, am I better off just adding the carriage bolts and will I do any more damage jacking up the outside beams. The deflection at its worst point is somewhere between an 1/8-1/4″. Anyone with any suggestions? The drywallers start one week from today so I basically have next weekend to fix this problem without tearing out there work.
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Did you follow your engineer's bolt pattern requirements? Proper hole sizes? What did you do?? Jack 'em up since you are still open and do it right.
*Craig, First off, you've got a good eye to notice the 1/8-1/4" deflection but thats very keen that you saw it. My question is this. What is the clear span of the beam? If you're talking about 16-20', I don't think that 1/4" is all that much. Does it bounce when you put weight on the floor above or is it just a squeak? I don't think I'd jack it up for fear of disturbing the other joists and possibly leading to more squeaks down the road. Maybe just a few more carriage bolts or possibly something like some Simpson strapping with a lot of hanger nails? I wouldn't drill too many holes for carriage bolts as that of course can weaken the beams (although I don't know how many holes you've drilled already. If they're not spaced like rivets on an airplane, I'd say you're OK.)Mike Rimoldi
*Unfortunately, I didn't get an engineer's bolt pattern requirement or hole sizes so I drilled to accomodate the carriage bolts and went with it. The span between supports is about 20 feet and I was planning on jacking up the center to even, putting two at that point, and then splitting the span and putting two on either side. Does this seem like a reasonable approach?
*The total span is about 30' with a 6"x6" column on either end and also one at the 10' mark (below where the ridge beam of the main roof sits - a 1-3/4"x18" times 2 microlam beam over a 20' cathedral ceiling). The deflection occurs in the 20' section between the midpoint support and one side of the house. My concern is that if it has sagged after only about 10 months, it is only going to get worse as the house settles, and, I'm not getting the full support that the beam was intended to give.
*Craig, What are they, 1/2" diameter carriage bolts? Your plan sounds good but I would watch how much force it takes to jack up the center to make all the beams evenflush. If it goes up very easily, you might consider some additional bolts. The thing I would observe when jacking it is if the outside beams move independently of the inner ones or does it appear that they are indeed secured together and move as a complete beam. Also, on the glulams I've used, I also drive quite a few 16d nails from both sides as cheap insurance. Sure, I know a few nails doesn't carry much weight when the load is a shear load but the idea of tieing the beam together to me makes sense and is what I see as cheap insurance.Mike
*You may wish to get the manufactures recommendation on bolt patterns.G-P specifies that a side-loaded, 4 piece LVL beam must be bolted with 2, 1/2" bolts on a 12" center, with the bolts being 2" from the top and bottom edges. (This will give a capacity of 675# per lineal foot [on each side] for the fasteners - it could be increased to 1012 plf by using 3 bolts, 12" oc)They also call out for the bolt hole to be the same diameter as the bolt, and to use washers under the head and nut.I have some question about using carriage bolts.My G-P literature doesn't get specific about the grade of the bolt required, but a carriage bolt is typically Grade 2 and a common hex bolt will be a Grade 5 (Grade 8 is typically automotive type use).I would get some specific manufacture's recommendation on this one.Terry
*thanks for the additional information. I'm going to call the lumber yard that I purchased the beams from and get the information you specified from them.What are your thoughts about jacking the beam up? I was planning to use (2) 2x12's on a hydraulic jack directly under the center of the beam. That will (I hope) allow me to raise the two outside beams flush with the two inside beams and than allow me to install my bolts.Thanks again for your information.
*Sounds like what Craig has got is the two outside M-Lams carrying separate floor loads alone and the interior ones are, by virtue of not being through bolted near center span, not carrying anything. Not good. Get some expert advise from someone who can discuss this with you face to face or better yet, visit the site and see exactly what you've done.Eric
*I would go ahead and try to jack the outer plys up and flush.My personal choice to force it up with boards cut slightly taller and drive the bottom towards vertical. It may require multiple boards, but you can lift it without the risk of a board kicking off a hydraulic jack that wasn't placed perfectly.Terry
*Never have I bolted microlams....They are usually just nailed with 20's...Never had your problem.....jack back to where yaa want them,,,then nail fasten to manufacturer specs....Next time...get your specs first and follow them.near the stream,aj
*I always just nail mine also, but I have never done a 4-ply beam.Georgia-Pacific requires 4-ply beams to be through bolted, with different bolt patterns depending on plf requirements.I believe a number of LVL manufactures require bolts with 4-plys, although I would still be spiking them in addition to the bolts.Terry
*Like we both are saying....get specs with your materials...and follow them. Brushing your teeth is cool too if anyone didn't know along with daily showers and BO Counteractants...near the freakin stream tyin the young pups shoes for em,aj
*Thanks for all of the suggestions. I've followed the advice and gotten the manufacturers spec from the lumber yard and that is 2 1/2" carriage bolts 12" on center with the holes drilled 2" from each edge. I plan to raise the beam back to flush using the board method as opposed to the jack and add the carriage bolts. To be on the safe side, I'm going to add the nails, too. Again, thanks for all the responses, you all have saved me a lot of heartache (and money) down the road.
*Forget the nails....Overkill is as bad as underkill!!!!!I have built many an aircraft...and it's even more true when yaa fly....near the stream,aj1/2" bolts I'm sure...
*AJ, What the hell, ya' worried about a little Kt? Where ya' been? Waiting for the new digs in Chicago, Sam
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I am framing a home and used built up micro-lam beams for the major cross beams. For the longest span the beam consists of four 1-3/4" x 12" micro-lams bolted together. I noticed (while trying to track down some floor squeaks) that the outside boards have sagged (I have joists attached to both outside beams). My conclusion is that I didn't put enough carriage bolts through to transfer bearing through to all 4 beams. I came up with two solutions 1) jack-up the two outside beams and then add carriage bolts to carry the weight through or 2) just add carriage bolts to prevent any further deflection.
My question is, I guess, am I better off just adding the carriage bolts and will I do any more damage jacking up the outside beams. The deflection at its worst point is somewhere between an 1/8-1/4". Anyone with any suggestions? The drywallers start one week from today so I basically have next weekend to fix this problem without tearing out there work.