some time ago i inquired about fastening some steel plate to the sides of some 100+ year old, full dimension, rough cut oak floor joists to stiffen them up. I've decided to sister them with like sized (2x8) wood instead. These are the second story floor joists and they are 2x8 and span 15.5 feet. I've got the ceiling out on the lower level and want to stiffen them up before i go back with new ceiling. My question is, what is the best way (and frequency) to attach them? Screws, nut and bolt, nail, glue, etc?? It's a balloon style house and i'll be able to set the new sisters up on the ledger board like the originals. My main concern is pulling them together in such a fashion as to best create a "oneness" .
thanks!