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walkereng
walkereng, Consultant
Category: Structural Engineering
Satisfied Customers: 2445
Experience:  Over 30 years of Structural Engineering experience.
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I have an 11” gh step supported by a 9.5” engineered I joist

Customer Question

I have an 11” high step supported by a 9.5” engineered I joist terminated on a load bearing wall. I cannot put a platform in front of the step. I would like to cut the I beam to form two steps, 5.5” risers, by an 8”deep step. To compensate for cutting the I beam I would attach (glue & screw) “sister” 2”x9” on each side of the stepped I beam, and run the sister between the load bearing walls (~7’). I would need to do this to three I beams for the width of the steps. Is this acceptable code and engineering wise?
Submitted: 1 year ago.
Category: Structural Engineering
Expert:  StructuralEng replied 1 year ago.

Hello. I can help. Can you post a sketch for me to look at?

Customer: replied 1 year ago.
Sorry for the delay. Please let me know if the attached drawing is adequate.
Expert:  StructuralEng replied 1 year ago.

Unfortunately, that violates prescriptive requirements for wood I joists, unless the notch occurs over top of the support. That abrupt change in geometry is a big problem for stress concentrations in a plywood or OSB web that is intended to carry shear only and not bending moment.

Customer: replied 1 year ago.
I understand, that is why the OSB of the beam is sistered on both sides with 2 bys. Are you saying the shear strength of the sisters, with the 5.5"step cut into them is less than the uncut I beam? Alternatives? To leave it alone is against code too.
Expert:  StructuralEng replied 1 year ago.

There isn't just shear at the section. There is also bending moment.

Customer: replied 1 year ago.
a possible solution is?
Expert:  StructuralEng replied 1 year ago.

You will need a different framing configuration.

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