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StructuralEng
StructuralEng, Consultant
Category: Structural Engineering
Satisfied Customers: 6749
Experience:  Structural Engineer
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I have an 18' span of supporting wall I am removing and replacing

Customer Question

I have an 18' span of supporting wall I am removing and replacing with a hidden beam set on top of ceiling joists. Beam will consist of (2) 14' & (2) 7' LVL's glued and screwed together. Ceiling joists will be bracketed to the beam. The 2 ends of the beam will set on top of ceiling joists that sit on existing supporting wall sections. 1 1/2' on each end will be supported. Can anyone support my thinking that this will more than support the ceiling? Ceiling joists span from exterior wall to exterior wall 28'. 14' on each side of the hidden beam.
Submitted: 1 year ago.
Category: Structural Engineering
Expert:  StructuralEng replied 1 year ago.
What size LVL? I would not personally do that without a full analysis and design of the fastener pattern. You have to transfer a lot of bending moment through shear in the fasteners.
Customer: replied 1 year ago.
Click image for a larger view.
Hover to zoom in.(2) 1 3/4" x 7 1/4" x 14' LVL 1.9E and (2) 1 3/4" x 7 1/4" x 7' LVL 1.9E screwed together in 3 rows, each screw 6" apart with 3" triple coated deck screws
Expert:  StructuralEng replied 1 year ago.
What is the span of the beam?
Customer: replied 1 year ago.
beam is doubled up so finished beam size is 3 1/2" x 21'. 1 1/2' on each end sits on supporting wall. Remaining 18' is supporting ceiling joists
Customer: replied 1 year ago.
Ceiling joists are 2x4's, 16" O.C. 14' span on each side extending to exterior walls.
Expert:  StructuralEng replied 1 year ago.
I would not do that without having the fasteners designed to transfer the moment between all the plies. And a 7.25" deep member is VERY shallow for a 21' span. Especially supporting 14' joists on each side.
Expert:  StructuralEng replied 1 year ago.
I can size the fastener pattern as an additional service, but I think you will need a deeper beam.
Customer: replied 1 year ago.
Let me double check the depth of the beam, 7 doesn't sound right to me now that you say that... one moment
Customer: replied 1 year ago.
Your right, it was 11 1/4" not 7 1/4". I apologize
Customer: replied 1 year ago.
Btw, only attic space above. no more than a 3/12 pitch hip roof. In northern Indiana. Not sure if that helps
Expert:  StructuralEng replied 1 year ago.
It doesn't support the roof, correct? Only the attic?
Customer: replied 1 year ago.
Correct
Expert:  StructuralEng replied 1 year ago.
Even with an empty attic live load of 10 psf and a dead load of 12 psf with full length beams, deflection will be almost 1.5"
Expert:  StructuralEng replied 1 year ago.
The beam is too small for the job. Once you start transferring moment through the fasteners it makes it worse.
Customer: replied 1 year ago.
What size beams would be needed to make it work?
Expert:  StructuralEng replied 1 year ago.
a triple 14" would keep deflection to a more reasonable level of 0.7"
Customer: replied 1 year ago.
What is the normal recommended deflection level?
Customer: replied 1 year ago.
one last question, I don't want to take up too much of your time... is there a calculator I can use online or a program I can download to calculate these loads for me?
Expert:  StructuralEng replied 1 year ago.
I'm sure that there is somewhere, but I don't use them and you need to fully understand all the assumptions that go into using them.
Expert:  StructuralEng replied 1 year ago.
span/360 for live load and span/240 for total load is a common limit.No problem. I'm happy to help. Good luck with your project.
Customer: replied 1 year ago.
ok thank you.
Expert:  StructuralEng replied 1 year ago.
Any time

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