How to Repair a Roof Joist

Written by shelly schumacher
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The roof joists in a house span across the ceiling, from the front to rear of the structure. The joists hold the ceiling in place and attach the roof and rafters to the exterior wall structure. A broken roof joist is a serious problem that requires immediate attention. If it is not repaired, it can cause the ceiling inside your home to sag and might result in a cave-in. Repairing a roof broken roof joist is not an easy job, and might be best left to a professional contractor.

Skill level:

Things you need

  • Tape measure
  • Circular saw
  • Construction adhesive
  • 16d nails, 3 inches long

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  1. 1

    Measure the broken joist with a tape measure. Keep in mind that it extends to the outside of the walls.

  2. 2

    Cut your new joist with a circular saw. It should be cut the same length as the broken joist. Additionally, if the broken joist is notched or cut to fit other objects such as walls trusses, the new one should have the same notches.

  3. 3

    Determine the accessibility to the broken joist. The new joist will need to be fed into the attic space so that it is next to the broken joist.

  4. 4

    Apply a construction adhesive to the broken joist on the side next to the new joist.

  5. 5

    Place the new joist next to the glued side of the broken one and nail both together. There should be two rows of nails, across the face of the board, one on top and another on the bottom. The nails should be attached every 6 inches.

Tips and warnings

  • Purchase a joist that is the same dimension as the broken one. For example, if you are repairing a 2-by-8 joist, you will need a new 2-by-8.
  • You may need to cut a hole in the ceiling to feed the new joist through.

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