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Discussion Starter #1
My wonderful neighbor who is a retired structural engineer designed a beam I can use to add 8' sliding glass doors to our lower level family room. He calculated a flitch beam of 1/2" x 6" steel between 2 x 6"s. Then I had a couple of contractors bid the project who both said that very likely a manufactured wood beam would be just as strong and much easier to work with. I don't want to ask my neighbor for more assistance, he's already been so generous, and engineering firms here are overwhelmed and taking a long time to get back to us (none have yet). I wonder if anyone here knows their LVL strengths or can point me to tables online.

The calculation is that the Live Load is 808 and Dead Load is 257 for a Total Load of 1065#/lf. There are a bunch of other calculations and abbreviations on his sheet that I don't understand but can post if needed. The beam can't be more than 6" high or we cut too much into the headroom. We don't mind having a weirdly wide beam that intrudes into the room if the LVL needs to be tripled (or more?).
 

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retired framer
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If all you have room for is 2x6, go with the engineer.
If you remove the 2 top plates will you have room for a 2x10 header.?
Do the ends of the floor joists land on this wall?
 

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Discussion Starter #3
We are already planning to remove the top plates in order to get 6". Yes, the ends of the floor joists land on this wall, as do joists for an exterior deck on the floor above. We can go much thicker than the designed flitch, which is ~4", but not higher than 6" (or not much, anyway - I suppose we could have a rough opening somewhat smaller than recommended if it's very very square?).
 

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You might want yo talk with your neighbor some more. Here is a part of a span table from weyerhauser. For 8 ft span, triple LVL beam 5-1/2” high ... total load is a whopping 461 pounds. Substantial increase for 7-1/4” beams if you have the headroom. If you use swinging doors with a column in the middle you can get better results.

7268A14D-172D-499A-9A02-FEC264E34C41.jpeg
 

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As an engineer - I would say that he would not be offended by an opportunity to discuss the benefits and drawback of any outside alternatives. That's what engineers live for... explore all possibilities and exhaust the bystanders...

Share the span table posted ^^ - he may not be familiar with some of the latest products and at the least will probably print a copy of the table for his files! (Or simply formulate the corresponding load coefficients so he can derive the answers in the future.)

Bring him a bottle and a smile... from all of us!
 

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Discussion Starter #6
Thanks for posting that table, Eddie. It looks like with my total load of 1065#/ft, I would need something close to a 71/4" triple LVL? I guess we should see if we can eek out another 1 1/2" in headroom, but we also need something slightly longer than 8' to span the door and supports, so then would need even deeper.
 

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retired framer
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Thanks for posting that table, Eddie. It looks like with my total load of 1065#/ft, I would need something close to a 71/4" triple LVL? I guess we should see if we can eek out another 1 1/2" in headroom, but we also need something slightly longer than 8' to span the door and supports, so then would need even deeper.
If you rip and tear the beam can replace the rim joist so you have plenty of room to do things that would not need an engineer, I would like to know what the contractors were suggesting,If they were suggesting just 2x6s they are the wrong contractors.
I have never met and engineer that wasn't apposed to ideas on how to do it different than there first suggestion.
 

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I fail to see why it would be so hard to go with the engineer neighbor's suggestion. How hard is it to get a piece of steel and drill holes in it... or specify hole locations and order it that way. And no, engineered wood will never be as strong and will likely have more deflection.

Step up would probably be a steel w-beam with sides packed out with wood.
 

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How hard is it to get a piece of steel and drill holes in it... or specify hole locations and order it that way. .
You really don't want to be drilling a couple dozen holes in half inch plate with a hand drill. Option B is a much better idea --- just specify size are location --- the steel supplier will have mills and drill presses to do it much easier.
 

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Discussion Starter #11
I do have a drill press, but still think I would order it pre-drilled.
Both contractors were hoping for some sort of manufactured LVL, not just 2x6s. But yeah, I'm not really sure why they think the steel is that big of a deal, especially since it can be assembled with the wood onsite.
A related question - is the span in the tables the opening, or the total beam length, or something in between? I.e., for an 8' door, do I look up an 8' length in the tables even though I'd actually order something closer to 106" (96" door + 2" for rough opening + 8" for width of two supports)?
 

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retired framer
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I do have a drill press, but still think I would order it pre-drilled.
Both contractors were hoping for some sort of manufactured LVL, not just 2x6s. But yeah, I'm not really sure why they think the steel is that big of a deal, especially since it can be assembled with the wood onsite.
A related question - is the span in the tables the opening, or the total beam length, or something in between? I.e., for an 8' door, do I look up an 8' length in the tables even though I'd actually order something closer to 106" (96" door + 2" for rough opening + 8" for width of two supports)?
if the window is 8 ft, that is a span and you would want 102" for your beam length.
 

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retired framer
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I do have a drill press, but still think I would order it pre-drilled.
Both contractors were hoping for some sort of manufactured LVL, not just 2x6s. But yeah, I'm not really sure why they think the steel is that big of a deal, especially since it can be assembled with the wood onsite.
A related question - is the span in the tables the opening, or the total beam length, or something in between? I.e., for an 8' door, do I look up an 8' length in the tables even though I'd actually order something closer to 106" (96" door + 2" for rough opening + 8" for width of two supports)?
You only add 2 inches for doors and when you get to double door you have to add more, but sliding glass doors are windows.
 

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. It looks like with my total load of 1065#/ft,
You are missing a very important detail. If you don’t pay attention to this, your house could collapse.

Twice now you have posted that your load is 1,065 pounds per linear foot. I’m taking that as a fact. So for your 8 ft doors, the total load on the beam will be 8,520 lbs.

You need to talk with your neighbor and verify what the calculated load actually is.
 

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Discussion Starter #15
You are missing a very important detail. If you don’t pay attention to this, your house could collapse.

Twice now you have posted that your load is 1,065 pounds per linear foot. I’m taking that as a fact. So for your 8 ft doors, the total load on the beam will be 8,520 lbs.

You need to talk with your neighbor and verify what the calculated load actually is.
Yes, that’s right. That is what he calculated and it seems right based on standards. We have a floor above with beefy mid-century framing, plus a large deck hanging off this beam. How would over-engineering the beam be a problem?
 

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Over engineering would only cause two issues: cost and size. My point was, the triple LVL from the weyerhauser chart would only hold a fraction of your load. You have a dimensional problem, you either need more height for the beam, or shorter span. Or buy your neighbor a beer.
 

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Discussion Starter #17
I didn't know that sliding doors take window rough in allowances, thank you! I also now see that standard size + rough in allowance = 8', so that makes the opening less than I had thought we needed. Now I need to re-measure what we have for the beam in case I used 2.5" needed for the rough in. Fingers crossed we have an inch or so more than I thought! :)
 

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I ran your 1065 PLF load on a 5.5" tall 1/2" steel flitch plate (it would not be a true 6" tall). My analysis says that the steel is severely overstressed, like over 40,000 psi when steel is only rated for 20,000 psi allowable load on a flitch beam. I think you should consult a different engineer than your retired guy if you plan to use a steel flitch plate.
 
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