How to Repair a Broken Roof Joist

A roof joist supports the weight of a roof and helps keep the ends of the rafters from splaying, making the structure stronger and more stable. When a joist is broken, it affects the strength of the entire roof. Joists can get broken during transport or in the process of construction. Repairing a roof joist should make it as strong as it was before it broke, making the entire roof and ceiling more stable.

2-by-4-inch lumber
Construction adhesive
Screws, 4 inches long
Drill

Instructions

- 1
  Cut two 2-by-4-inch boards to use as splints on the joist. The longer the 2-by-4s are, the more solid the repair will be.
- 2
  Apply construction adhesive on one long face of all the 2-by-4 boards.
- 3
  Put one of the 2-by-4s on the side of the broken joist, so the break is at the center of the 2-by-4, with the construction adhesive pressed against the joist.
- 4
  Drive screws through the 2-by-4 and into the truss with 4-inch-long screws. Drive the screws in far enough to secure the 2-by-4 but not so far that they pierce the other side of the joist.
- 5
  Put the other 2-by-4 on the opposite side of the joist so that the joist is sandwiched between the two 2-by-4s. Drive 4-inch-long screws through this 2-by-4 and into the joist. Drive these screws all the way in, through the 2-by-4, through the joist and into the first 2-by-4 that you installed in Step 3.
- 6
  Return to the screws that you inserted in in Step 4, and drive them in the remainder of the way so that they pierce through the joist and into the other 2-by-4.
- 7
  Insert more 4-inch-long screws down the length of both 2-by-4s. The repair will be stronger with more screws holding it rigid.

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