There is a joint in my attic where 4 beams or rafters meet. Someone used a 2x4 to support one of the beams, but it did not work because the beam was in two sections.As you can see in the pictures, there is a couple of inches in sag, and the rafters are beginning to pull apart. I was considering putting a 2x6 across the ceiling joists on top of a wall, then hammering in a 2x4 to "jack" up the joists. I am new to this forum and not a construction expert. Any advice would be greatly appreciated.
It looks as though this thing was built out of scraps pieced together. There is just no way this is ever going to be sound the way it is.
I think your best course of action is to build some temporary supports to keep the roof from collapsing, pull out the substandard rafters and rebuild using correctly sized lumber, supported properly.
If you're in doubt about how to do this, you may want to hire a professional. I wish there was some quick and east fix but unfortunately I just don't see that in this case.