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Can LVL beams be used with spacer blocks in the center to flush the LVL material up on each exterior side? For example when using two 1-3/4" thick LVL's with 2x6 trimmer material it only comes out to 3.5", so can you use 2" spacer blocks between each LVL to flush them up? Or must they be glued & nailed together with an artificial spacer material on one side?

As backstory, there was no specification on whether the LVL needed to be sistered & nailed per typical LVL nail schematics from the engineer. They didn't even ask the floor joist length which was bothersome. Both lumber yard and building department seemed okay with having the space in middle be hollow, but I was curious in terms of support if the LVL in a box header format functions differently. I don't see how because it's bearing equally on trimmer studs, and now has a larger footprint in terms of load point. Wanted to know if builders or engineers had third opinion.

Edit to add: Engineer okayed this. Said that technically one LVL was enough for the load. When I asked if this would work for two when needed he said "I don't see why not, as long as they can not separate from one another and touch at same points" which is what the structural lags and top plate above the LVL do.

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  • Presumably you had an engineer specify the LVL size? Dec 5, 2021 at 7:03
  • Yes, there was no specification on whether the LVL needed to be sistered & nailed per typical LVL nail schematics. Both lumber yard and building department seemed okay with having the space in middle be hollow, but I was curious in terms of support if the LVL in a box header format functions differently. I don't see how because it's bearing equally, and now has a larger footprint in terms of load point. Wanted to know if builders or engineers had third opinion.
    – CCCBuilder
    Dec 7, 2021 at 14:08
  • Do you have the spec sheet from the LVL manufacturer? I’ve always seen the manufacturer require that individual members are nailed or bolted together for a built up beam. Dec 7, 2021 at 16:00
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    @RibaldEddie yes, and I haven't seen a spec sheet where fastening multiple plies is not required
    – P2000
    Dec 7, 2021 at 17:26
  • Is this a typical situation that LVL is used in parallel to a wall as the edge beam? What was the call out (of the edge beam) by the engineer, 2- 1 3/4" x XX" LVL?
    – r13
    Dec 7, 2021 at 17:27

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No, you wouldn't space out the beam members. They generally need to remain fixed together according to the fastener schedule provided by the manufacturer or architect. You'd then fur out to the thickness of the wall. Even if this isn't a requirement, it's what I'd do. You don't want to have to try and tie heavy members together with fasteners when they're spread.

It's common practice to put the beam flush to one face of the wall, mostly so you don't have to fur out both and possibly insulate between. Add whatever lumber strips are convenient. A few fasteners will not cause structural concerns.

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  • Yes, "They generally need to remain fixed together" is my understanding too, with sometimes allowance for a 1/2in plywood sandwich up to make things flush, but what do you mean with "You don't want to have to try and tie heavy members together with fasteners"?
    – P2000
    Dec 7, 2021 at 17:28
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    Edited to clarify. Usually when beams are doubled it's required that they be connected mechanically using appropriate fasteners. The new beam then becomes greater than the sum of the parts in terms of load rating. If you space them out you'd have to come up with the equivalent fastener of a much longer length, and you'd have to provide spacer blocks that are structurally suitable. I wouldn't risk degrading beam performance with such an approach, as a matter of best practice if not specific requirement.
    – isherwood
    Dec 7, 2021 at 17:51
  • I've always done this as well but I'm very curious what the difference is in a situation where each LVL is bearing the same? There is a flat top plate above the lvl that holds the top of the lvl from pulling out, blocks in the center void with structural lags, and then the bottoms are secured to the load bearing posts on each end. The footprint of weight is now distributed more equally than if one side of the wall had both lvl flushed up.
    – CCCBuilder
    Dec 11, 2021 at 14:47
  • Weight distribution isn't really a concern here. They're on the same trimmer studs or posts, and it doesn't really matter where they sit. There are certainly many ways to secure the beams. I'm only relating common practice. Where twin LVLs are specified they usually have an attachment schedule. YMMV.
    – isherwood
    Dec 11, 2021 at 16:21
  • Headers in exterior walls have their cavity on the inside rather than between the plies so that insulation can be applied after framing. Multiple plies of beams are fastened to each other to handle side loads (joist or beam hangers); also if point loaded by joists/cross-beams/posts, I believe to avoid buckling along the depth or shifting of the plies, causing one ply to bare more load than the other.
    – P2000
    Dec 12, 2021 at 1:12

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