I have a house that was built in 1920. the attic measures 18' wide and 40' long. The joists are true 2x8's (not today's 1-3/4" x 7"). They run in the 18' direction and are 16" O.C. I am considering adding a small staircase up to the attic and making a game room up there (pool table, poker table). The pool table weighs 500 to 600 lbs., but the room will not be used on a daily basis.
My question is, what type of plywood is exceptable for the flooring? I am thinking of using either 1/2" or 3/4" OSB, but I am told that I am a fool to use anything other than CDX.
Also, would adding a few 2x4's running perpendicular to the joists add any support? What about adding a few 2x4-18' in the area of the pool table, is this necessary?