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StructuralEng
StructuralEng, Consultant
Category: Structural Engineering
Satisfied Customers: 6690
Experience:  Structural Engineer
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, I have a roof ridge that uses a perpendicular 2x4

Customer Question

Customer: ***** *****;
JA: Thanks. Can you give me any more details about your issue?
Customer: I have a roof ridge that uses a perpendicular 2x4 support and two supports off at an angle. They are close to each other at the bottom. I want to replace that with a if you hold up the three middle fingers of your hand and spread your fingers - it looks like that kind of a shape. I want to replace that support with a beam underneath which has a span of about 6'; it will open the area up instead of being blocked from bottom of attic floor to the top. An engr told be a 2x8 header two 2x8's with 1/2 material inbetween) But I want to use structural steel to make the height smaller
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Customer: Yes, but to make it simple if you can answer it; for a 6 foot span, can a steel I beam 3" height 5.7lbs per foot support the same weight as a 2x8 double header?
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Submitted: 10 months ago.
Category: Structural Engineering
Expert:  StructuralEng replied 10 months ago.

Hello

Expert:  StructuralEng replied 10 months ago.

Do you have any pictures you can post?

Customer: replied 10 months ago.
support_1.png is a picture to show the three supports that I hate
support_2.png is a drawn over picture to show the support beam position
ridge Support is picture of what structural engr sent mebut I need 6' and I want to reduce the height
because the height of available space allows me more room to position duct pipe for ac system
Im trying to get rid of the plenum boxes.
Customer: replied 10 months ago.
The other side of the ridge board doesnt go very far back and the side rafters are relatively short in length
ridge board goes about 4' on other side of 2x4 support.
Customer: replied 10 months ago.
the ridge is sitting at about 18" to 24" from one end
so the load is not in the middle of the span
Expert:  StructuralEng replied 10 months ago.

Thank you for the attachments

Customer: replied 10 months ago.
I was looking at this web site for structural steel
http://www.metalsdepot.com/products/hrsteel2.phtml?page=steel%20beamAt bottom of attached pic
B1357 is 3" high I beam with 5.7lbs metal per linear foot
B1477 is 4" high I beam with 7.7lbs metal per footWhat kind of steel I beam can replace the load capibilities of a double 2x8 header support beam like in the Engineer's drawing I provided earlierthanks a lotDennis
Expert:  StructuralEng replied 10 months ago.

I would use W4x13 so that lateral torsional buckling is not a concern.

Expert:  StructuralEng replied 10 months ago.

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

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