I am replacing part of a floor because of water damage. I have removed three layers of flooring. The joists were unaffected by the rot (as was the bottom floor, but I removed it anyway).
I only intend to put in one or two layers of 3/4" plywood for the new subfloor. I don't want to build up ~2.75" inches of flooring and try to match the thickness of the original floor. Instead, my plan is to sister the joists in this area in order to lift them to the appropriate height. So the entire weight of the floor will rest on top of the new sisters.
The sisters will cover only ~6 ft of the original joists' ~9 ft span. The original joists are undersized by today's standards (they are 2x5s [4.5" actual—never seen that before!] spaced 16" o.c.), but there is no noticeable sag, and replacing the entire floor is out of the question at this point. So I'm not looking for the sistering to create a stronger composite system, but simply to build up the floor.
Is it enough to glue the joists and nail them? (If so, is a couple of 8d common nails every 8 inches good?) Or is there occasion to use screws or bolts also?