Sister Cracked Floor Joist

On both sides of the problem area.

Sister cracked floor joist.

But it s usually best to run the sister joist over the entire span. Slip an old work metal joist hanger onto the end of the joist. Cut a sister joist the same length as the damaged joist. When the sagging joists are level apply a generous bead of construction adhesive to the existing joist.

Pump up the jack until the post pushes closed the crack in the joist. If a crack or sag is isolated to one area the sister joist should extend at least 3 ft. I suppose somewhere in the world there are floor joists that need to be repaired that have wide open clear joist bays with no pipes wires or obstructions. Structural screws and joist hangers if applicable.

Squeeze a generous amount of carpenter s glue into the crack in the floor joist. Tools materials required. 2 x 4s together to make a cross beam then place the beam perpendicular to the joists near one end of the joists. Properly sistering floor joists is very important and should not be rushed to save time.

Place it next to the damaged joist with the crown side up. Framing lumber or laminated lumber if needed for strength. Since this is a repair of a faulty or damaged floor joist it is imperative to do this project correctly and there are a few big mistakes to avoid. I recently had to repair a broken floor joist that had cracked.

If needed notch the bottom edge of the sister joint so it fits over the foundation or beam.