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StructuralEng
StructuralEng, Consultant
Category: Structural Engineering
Satisfied Customers: 7156
Experience:  Structural Engineer
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I need to size a beam house. the span will be 279 inches and

Customer Question

I need to size a beam for my house. the span will be 279 inches and the joist length is 20 feet 12" on center 2x12 joists
Submitted: 1 year ago.
Category: Structural Engineering
Customer: replied 1 year ago.
to be more specific this beam supports the second floor only and will be supported on both ends using appropriate methods. The tributary length as I understand it is the total length of the floor joists. That length is 20 feet using 2x12's that are 12" on center. the length of the beam will need to be 279". I would like this beams depth to be less than 12" so it can be recessed into the ceiling and hidden. I'm open to a steel I-beam if necessary but would prefer an engineered wood option. The floor load is 3/4 inch plywood and carpet-the ceiling is 1/2" drywall.
Expert:  StructuralEng replied 1 year ago.

Hello. I can help. Do you have any sketches you can share?

Customer: replied 1 year ago.
I have attached a drawing. I'm considering a w10x26 steel I-beam however if I could size a glulam that has a depth of 12" or less that would be easier to install.
Expert:  StructuralEng replied 1 year ago.

Thank you for the sketch

Expert:  StructuralEng replied 1 year ago.

A glulam would need to be a 5.125" x 16.5" 24F-V4

Expert:  StructuralEng replied 1 year ago.

Wood just has to be much deeper, because steel is 15 times more stiff.

Customer: replied 1 year ago.
Thank you for the info. Am I correct in my spec of a w10x26 or could I have a smaller steel I-beam?
Customer: replied 1 year ago.
If I could size a slightly smaller I-beam it would be easier to install but I definitely don't want any ceiling sagging!!
Expert:  StructuralEng replied 1 year ago.

A W10x22 will work for L/240 deflection (1.1"), but you'll need a special detail to let the joists brace the beam laterally.

Customer: replied 1 year ago.
This is what my contractor recommends
Customer: replied 1 year ago.
obviously not to scale lol
Expert:  StructuralEng replied 1 year ago.

That is a reasonable detail.

Expert:  StructuralEng replied 1 year ago.

Hello, how are you doing? Do you have any other questions on this topic? If you could rate my answer, I would appreciate it.

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