Sister Cracked Floor Joist

Position a 2x4 post and hydraulic jack directly beneath the cracked end of the joist.

Sister cracked floor joist.

Squeeze a generous amount of carpenter s glue into the crack in the floor joist. On both sides of the problem area. Framing lumber or laminated lumber if needed for strength. When the sagging joists are level apply a generous bead of construction adhesive to the existing joist.

Fixing broken cracked sagging floor joists. Structural screws and joist hangers if applicable. A severely cracked or sagging floor joist can get worse over time causing the floor above it to slope or become unleveled. Cut a sister joist the same length as the damaged joist.

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. If a crack or sag is isolated to one area the sister joist should extend at least 3 ft. Properly sistering floor joists is very important and should not be rushed to save time. If needed notch the bottom edge of the sister joint so it fits over the foundation or beam.

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. 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. Place it next to the damaged joist with the crown side up.

Pump up the jack until the post pushes closed the crack in the joist.