Sistering to existing joists to reduce joist depth

1) I may have to do the same thing myself in my COVID basement gym. My fuzzy hair rubs on the ceiling when I use the elliptical machine.

2) Your concern for the 1' "development" length is justified in my opinion. I'd be surprised if that got the job done.

3) In this context, "development" = a connection with both moment and shear capability. I feel that the connections should be designed explicitly for those demands. In this thread, among others, I've done a reasonable job of articulating my own, personal view on how this is best handled. As always, there's more than one way to skin a cat.

4) Given that you already plan to sister on two sides, I'd give some serious thought to the solution shown in the second sketch below. Numbers scmumbers; it's tough to beat actually taking the new pieces out to bearing.

I like the idea of blocking, I think I'm going to reduce the length of the cut down beam to allow for development.

Neat idea, but you don't bring up serviceability in your discussion. Sure, it can support the loads, but how soft is that floor going to be now? He may get his golf simulator, but what's his wife going to say when their bedroom floor turns into a trampoline? Check deflections and vibrations with your new set up to make sure it's going to be acceptable.

I may not be contributing a solution, but after some thought, I do have some questions:

On what basis were the staggered nailing between the 2x6 and 2x10 designed?
I believe that the nails, and their spacing has to be detailed to carry the maximum shear developed in the span. There is no moment transfer between the 2x10 and 2x6 joist. Is this correct?


Also, what is the purpose of the nails to the end of the 2x10 original joists?
These nails are not connecting any new element to the existing joist.
So what is their purpose/design?

Thank you.