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StructuralEng
StructuralEng, Consultant
Category: Structural Engineering
Satisfied Customers: 6689
Experience:  Structural Engineer
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I have an existing load bearing wall supporting a floor that

Customer Question

I have an existing load bearing wall supporting a floor that has a 4" x 8" support beam running 18'. I want to open the wall 12' span. Can I use a 4"x 4" beam under the current support beam for the 12' opening?
The city approved a 3 1/2" x 11 3/4" LVL for the opening not know that there was an existing beam 4" x 8" beam.
Submitted: 11 months ago.
Category: Structural Engineering
Customer: replied 11 months ago.
The load bearing wall is also supporting a wall on the upper floor but not supporting the roof. The home is 18' wide and this is a 1.5 story home so the upper floor wall peaks at 8' and tapers down to 2'
Expert:  StructuralEng replied 11 months ago.

Hello.

Expert:  StructuralEng replied 11 months ago.

Unfortunately, a 4x4 under a 8" beam is not the same as a 12" beam.

Customer: replied 11 months ago.
Is there another alternative?
Expert:  StructuralEng replied 11 months ago.

That involves keeping the existing beam? That beam is only

Expert:  StructuralEng replied 11 months ago.

30% as stiff as the 11.25" LVL. You would three of them.

Customer: replied 11 months ago.
that I understand. If I keep the existing 4x8 beam then I would would need 2 more 4x8 beams so that the result is effectively equal to 4"x24" (3-4x8s) vs one 3.5x11.25 LVL?
Customer: replied 11 months ago.
If that is true then I should be able to use a smaller LVL under the existing 4x8. what is the minimum height of the LVL that I could use under a 4"x8" beam for a 12' span that is equvialent in all aspects to a 11.25" LVL?
Expert:  StructuralEng replied 11 months ago.

That existing 4x8 doesn't buy you any height reduction. Using 3 4x8 is not the same as using a single 4x24. It's very different. The existing 4x8 will get you down to a 3.5" x 10" LVL, but it's 9.25" or 11.25". There is no 10" LVL.

Expert:  StructuralEng replied 11 months ago.

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

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