I am finishing a basement room beneath my living room and I want to reinforce a bouncy floor. This 90-year old floor has 2x6 joists on 24" centers, 2 layers of 1x6 T&G subfloor on diagonal,under 1/2" hardwood flooring. The span from center beam to sill is 10 feet. The joist bottoms are only 85" off the basement slab and I want to preserve every inch of headroom. Without going to larger joists, would I be better off adding a set of 2x6 joists reducing the centers to 12", or would sistering 2x6s to the existing joists be better. What about blocking or bridging? My first thought was adding the joists to reduce the interval and blocking the results. If blocking or bridging, would mid-span be adequate or should I block/bridge on 3' intervals? Thanks.