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StructuralEng
StructuralEng, Consultant
Category: Structural Engineering
Satisfied Customers: 6689
Experience:  Structural Engineer
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Trying to figure out what size steel beam I need for my

Customer Question

trying to figure out what size steel beam I need for my residential rehab.
JA: OK. Tell me a bit more about what's going on so we can help you best.
Customer: I have a 22'1" span with two LVL's sistered together in place currently. 12" high x 1.75" wide each, and they are bowing under the weight of the second and third floor. House was redesigned mid plans, after LVL's were in place, now I'm trying to remedy the situation
JA: Is there anything else important you think the Structural Engineer should know?
Customer: third floor walls are inset 5' from exterior side walls, which isn't carrying the load down correctly to the beam in place......
Submitted: 3 months ago.
Category: Structural Engineering
Expert:  StructuralEng replied 3 months ago.

Hello

Expert:  StructuralEng replied 3 months ago.

I can help

Expert:  StructuralEng replied 3 months ago.

Do you want the properly sized LVLs?

Expert:  StructuralEng replied 3 months ago.

Is it supporting the second and third floors?

Is there an attic, too?

What is the joist length on each side of the beam?

Will it support any ceramic tile?

Customer: replied 3 months ago.
I think I need to replace the LVL's with either steel? The third floor is usable space, considered an attic. Not sure off the top of my head what the joist length is on each side, but one is longer than the other. I've attached a few pics, and yes, there will be ceramic tile in the master bath, and wood floors throughout. Load is carried all the way down to the basement with beam, load bearing wall, and lolli columns. It's a unique and tricky situation with the front door being where it is and the LVL's snugging next to it.......that's something that cannot be changed. Thoughts? Will a flitch plate outside the LVL's work bolted through????
Expert:  StructuralEng replied 3 months ago.

But this beam itself is supporting the second and third floors only, correct?

Expert:  StructuralEng replied 3 months ago.

You said snugged next to the front door. Is it parallel or perpendicular to the front door?

Customer: replied 3 months ago.
Second and third floors, correct. And after just looking at the plans, the third floor is inset only 3'6", not 5'. If you look in the second picture I attached, the front door (green temporary door) you can see the LVL runs perpendicular.
Expert:  StructuralEng replied 3 months ago.

Can you estimate the joist length on each side?

Customer: replied 3 months ago.
approximately 8' on one side, 15' on the other. Did you see the pics to get a better understanding of what I'm talking about?
Expert:  StructuralEng replied 3 months ago.

I did

Expert:  StructuralEng replied 3 months ago.

You really need a 7" x 24" 2.0E LVL to limit deflection to L/600 for the tile.

Expert:  StructuralEng replied 3 months ago.

You would need a MC12x50 on each side of the existing wood beam

Customer: replied 3 months ago.
you're saying basically doubling the size of the two beams currently sistered in place? The 7"x24" would be one beam or would I need two of them sistered together? What about steel, or even flitch plates as an option?
Expert:  StructuralEng replied 3 months ago.

It could be a 3.5" x 24" on each side of the existing.

Expert:  StructuralEng replied 3 months ago.

I listed the steel channel you would need on each side.

Customer: replied 3 months ago.
Ok......so there's no confusion. So I can replace the current LVL set up with the 7"x24" LVL's with the MC 12x50 on each side? Is there any remedy that can be done with the current LVL's in place using steel channel or plates?
Customer: replied 3 months ago.
I want to know if I just use the existing LVL's that are in place, if the MC 12 x 50 is enough to support the load, or do I have to redo everything that is there?
Expert:  StructuralEng replied 3 months ago.

If you use the 7" x 24" LVL, then you don't need the channels.

Expert:  StructuralEng replied 3 months ago.

Adding the two channels would be if you leave the existing LVL in place.

Expert:  StructuralEng replied 3 months ago.

Do you have any other questions for me on this topic? If you could rate my answer, I would appreciate it.

Customer: replied 3 months ago.
I do actually. Most likely going to go the route of the steel channel. Would you happen to know how many carriage bolts are needed without ruining the integrity of the LVL?
Expert:  StructuralEng replied 3 months ago.

I can do that calculation and provide a sketch as a premium service. I will submit the offer now. If you accept it, I'll need about 2 hours to get it together.

Expert:  StructuralEng replied 3 months ago.

I submitted the offer. I'll need to know where the top of the channels are relative to the bottom of the joists.

Customer: replied 3 months ago.
Instead of doing the channel, what thickness of steel would be needed to just do a plate on each side? Then sandwich all that together with two more LVL's to hang joists from?? Of course, carriage bolt all that together....
Expert:  StructuralEng replied 3 months ago.

What is the maximum depth of plate that you can handle there? Just to let you know, the plates will be heavier than the channels since the steel is not as efficiently placed.

Customer: replied 3 months ago.
In trying to keep the current LVL's in place, max depth would be the current 12".
Expert:  StructuralEng replied 3 months ago.

What is the exact depth? 11.25" or 11.875"

Expert:  StructuralEng replied 3 months ago.

You would need a 1 7/8" x 12" plate on each side full length.

Customer: replied 3 months ago.
1 7/8 seems very thick! I did mention that LVL's would be placed outside that to hang joists from right??
Expert:  StructuralEng replied 3 months ago.

Yes, but the stiffness of the wood is not high enough to compete with the steel, so it will not attract load. I said the plate would be heavier, because a plate is not an efficient use of steel in bending.

Expert:  StructuralEng replied 3 months ago.

And 12" isn't much depth to support that much load over a 22' span.

Customer: replied 3 months ago.
Believe me, I'm not discounting your expertise at all.....just shocked! Let me think about this for a bit, perhaps I'll have you draw up the bolt pattern for both applications.....plate and channel.....
Expert:  StructuralEng replied 3 months ago.

No problem. To give you a sense. Each channel weighs 50 pounds per foot. The plates have the exact same moment of inertia (so they will have the exact same deflection), but they weigh 77 pounds per foot.

Customer: replied 3 months ago.
If I wanted to get crazy and change out the current LVL'S for say 18" depth by 1.75" wide......how much does that change my scenario???
Expert:  StructuralEng replied 3 months ago.

If you wanted to take out the current beam, I would recommend installing a properly sized I beam with a detail to allow joist hangers into the side.

Expert:  StructuralEng replied 3 months ago.

That would actually make the total weight of the beam drop to 40 pounds per foot, instead of 100 pounds per foot for the 12" channels or 150 pounds per foot for the plates.

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