Sister Cracked Floor Joist

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

Sister cracked floor joist.

But it s usually best to run the sister joist over the entire span. If a crack or sag is isolated to one area the sister joist should extend at least 3 ft. Structural screws and joist hangers if applicable. 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.

Pump up the jack until the post pushes closed the crack in the joist. 2 x 4s together to make a cross beam then place the beam perpendicular to the joists near one end of the joists. Fixing broken cracked sagging floor joists. A severely cracked or sagging floor joist can get worse over time causing the floor above it to slope or become unleveled.

Squeeze a generous amount of carpenter s glue into the crack in the floor joist. Position a 2x4 post and hydraulic jack directly beneath the cracked end of the joist. Place it next to the damaged joist with the crown side up. Properly sistering floor joists is very important and should not be rushed to save time.

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. Framing lumber or laminated lumber if needed for strength. 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.

I recently had to repair a broken floor joist that had cracked.