Strengthen Floor Joists From Above
Tack a beam under the sagging joists.
Strengthen floor joists from above. Set a hydraulic jack and post under the beam and jack up the joists about 1 8 in. The nice thing about a beam and. Add an additional row of fas teners midway between the joists to pull the layers tightly together. Nailing two 2x4s together will work to span about three joists unless the sag is under a weight bearing wall.
As incremental parts of a building s structure joists are not easily replaced. You can however strengthen the joists by securing another length of wood to the existing joist called sistering. Choose ring shank nails or screws that are long enough to penetrate the joists by 11 2 in and space them every 6 in. A day until they re level.
Lay the new sheets perpendicular to the floor joists and orient panel ends over joists. Sistering is the process of adding a new joist next to each existing joist. Jacking them up too fast may cause cracks in the walls and floors overhead.