Walk across the floor in two of our rooms and the cabinets/book cases shake.
No...I'm not that heavy.
Current joists are 2x12, 16 inch on center, on 16 to 18 foot spans. There is X-bridging with metal straps (not coiled type) already in place.
Any ideas how to stiff up the floor? Would adding blocking as well between joists give any additional rigidity?