Increasing Moment of Inertia

[FEM4Structures]

good afternoon!
Had a contractor who bored 3” hole in four 2x6 wall studs that are at 24” o/c. Pipe runs horizontally through the studs before turning vertical through top double plates. If I were to increase the section modulus of the studs by adding 3/8” OSB sheets on both faces of the wall, how will that help the wall and studs to reclaim the material lost as a result of oversized bored hole?

Thanks,

FEM4Structures

 

[jayrod12]

Where is the hole? Near the top, bottom, mid-height? Inside face, outside face, centered in stud depth?

 

[SRCELL]

Simpson makes compression straps and stud shoes that could help you out too.

 

[Enable]

Is this an interior or an exterior wall? Are you trying to restore both axial integrity and bending (exterior) or just axial (interior)?

In either case, the calculation is straightforward. For axial, the additional strength is the cross section of the OSB. For bending, you would calculate the stiffness of the combined elements at the hole opening using the parallel axis theorem and compare the new moment capacity to your design loads.

The above assumes the fasteners are such that they can transfer the load without shearing (probably easy to satisfy). But I would be concerned about bearing in the OSB as it is a pretty weak material / any significant load on those fasteners and the immediate area around them will cripple causing movement in the assembly. Because of this I probably would go with plywood; OSB is not a great material when strength is actually needed.

Though as SRCELL notes, you may even be better to go with a prefabricated solution such as those produced by Simpson Strong-Tie. At least there you have confidence that the published literature takes such crippling issues into account.

As an aside, this sounds like a house and loads are usually pretty trivial. I have seen homes stay completely up-right after contractors cut all the studs of a bearing wall, not even cracks in the drywall in the floors above. Not recommended…but basically saying almost anything will work here despite what I said above.