In this video, This Old House general contractor Tom Silva helps a homeowner repair a cracked floor joist.
- Squeeze a generous amount of carpenter's glue into the crack in the floor joist.
- Slip an old-work metal joist hanger onto the end of the joist.
- Position a 2x4 post and hydraulic jack directly beneath the cracked end of the joist.
- Pump up the jack until the post pushes closed the crack in the joist.
- Fasten the hanger to the beam with hanger nails.
- Use a cloth to wipe off any excess glue from the joist.
- Install cross-bridging or solid blocking between joists to help stiffen the floor.
- When notching a joist, all notches should fall within the first or last third of the joist. Never cut a notch into the center third of a joist.
- The depth of the notch shouldn't be more than one-sixth the height of the joist.
- The length of the notch shouldn't be more than one-third the height of the joist.
- Notches should be cut straight and clean with radiused corners.
- Reinforce a notched joist by attaching a ¾-inch plywood strip.
- Cut the plywood strip at least as wide as the joist and secure it with construction adhesive and nails.