Sister Cracked Floor Joist

Cut a sister joist the same length as the damaged joist.

Sister cracked floor joist.

When the sagging joists are level apply a generous bead of construction adhesive to the existing joist. Slip an old work metal joist hanger onto the end of the joist. I recently had to repair a broken floor joist that had cracked. 2 x 4s together to make a cross beam then place the beam perpendicular to the joists near one end of the joists.

A severely cracked or sagging floor joist can get worse over time causing the floor above it to slope or become unleveled. Tools materials required. But it s usually best to run the sister joist over the entire span. Position a 2x4 post and hydraulic jack directly beneath the cracked end of the joist.

On both sides of the problem area. Squeeze a generous amount of carpenter s glue into the crack in the floor 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. Framing lumber or laminated lumber if needed for strength.

Pump up the jack until the post pushes closed the crack in the joist. Place it next to the damaged joist with the crown side up. If needed notch the bottom edge of the sister joint so it fits over the foundation or beam. Properly sistering floor joists is very important and should not be rushed to save time.

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.