How To Shore Up A Split Rafter By Using Support Pieces

Posted on: 16 October 2015

A split in a rafter beam can be a serious problem, especially if your home's roof is subject to significant stress caused by snow accumulation. That's why you should take time to repair the damage and restore your roof's strength. Below is what you need to know about shoring up a split rafter with a couple of support pieces you can build and install yourself:

Shoring up a split rafter - Tools and materials needed

  • 2-inch by 6-inch pine board, 12-foot length
  • Adding machine tape or drywall tape
  • Packaging tape
  • Chop saw or circular saw
  • Pencil
  • Electric drill with screwdriver bit
  • 4-inch wood screws
  • Measuring tape
  • Wood clamps
  • Construction adhesive tube
  • Caulk gun

Shoring up a split rafter - Step-by-procedure

1. Determine the angle of the cut - To provide the most effective support, the support pieces you make in the next step need to fit flush against the roof decking and the ridge board, the long horizontal board that runs along the length of the roof's ridge. Measuring the angle between the top end of the rafter and the ridge board is necessary to cut a duplicate angle on the support pieces.

To measure the angle, align a two-foot strip of adding machine tape or drywall tape along the long bottom edge of the rafter, then tape it in place using a couple of small lengths of packaging tape. Next, align a 1-foot strip of adding machine or drywall tape along the vertical edge of the ridge board, and tape it to the other piece of paper where the two strips intersect.

When you are finished taping, carefully remove the connected strips of paper from the broken rafter, then lay them on top of a new 2-inch by 6-inch piece of pine lumber. Tape the paper in place on top of the board, being careful to align the longest strip so it matches the board's longest dimension. Use your pencil to trace along the line formed where the angled strip of paper crosses the board. Finally, use a chop saw or circular saw to make a diagonal cut along the line. Remove the paper and dispose of it.

2. Measure and cut the board to length - Once you have sawed off the angled piece, the next step is to determine the length of the board. The board's length should exceed the length of the split by at least a foot, preferably more if possible. Measure the split from end-to-end, then add the extra foot or additional length to the dimension. Next, measure and mark off the dimension on the board, beginning at the point of the angled end. Use your saw to make a perpendicular cut across the board at the mark you just made.

3. Create a duplicate support piece - After finishing the first support piece, you need to create an exact duplicate that will be attached to the opposite side of the split rafter. Test fit both pieces to ensure they will fit the space on both sides of the rafter.

4. Glue the support pieces to the rafter - Apply a "zig-zag" ⅛-inch line of construction adhesive all-along one flat side of the support pieces; be sure the board is dry and clear of grease, debris or other substances that might reduce its adherence.

After applying the adhesive, push the first support piece into position along the rafter. Be sure the angled end near the ridge board is oriented properly and is firmly inserted into the narrow space between the ridge board and decking. Ask a helper to hold the support in place, then attach the second support piece using the same technique as the first. Just be sure you apply the adhesive to the correct side of the board.

After you have applied both support pieces to the split rafter, use at least two wood clamps to "sandwich" the broken rafter and support pieces together. Keep the clamps in position for at least 48 hours to ensure the adhesive has dried completely.

5. Finish the reinforcement with wood screws - After the support pieces have been glued to the split rafter, use an electric drill to drive 4-inch wood screws through the boards. Space the screws approximately 2 inches apart and drive them into the wood on both sides of the repair.

If you find your roof is in need of other more extensive repairs, contact a professional roofing contractor