How to Repair a Split Top on an Acoustic Guitar

Written by wade shaddy
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How to Repair a Split Top on an Acoustic Guitar
Fix a split in your guitar by adding a spline. (acoustic guitar image by Jeffrey Zalesny from

Acoustic guitars are usually made from solid pieces of spruce. The pieces are very thin and straight-grained, which can lead to cracking over time. Sometimes the instrument is dropped or damaged by too much string tension. Whatever the reason, if you have a crack or split in the top of your acoustic guitar, you can fix it before it gets worse by adding a spline. A spline is a thin piece of wood that acts as a filler and gives the guitar something for wood glue to bond with.

Skill level:

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Things you need

  • Utility knife
  • Masking tape
  • Tape measure
  • Spruce wood, 1/4-by-2-by-12-inches
  • Sanding block with 100-grit sandpaper
  • Wood glue
  • Mallet, nylon head
  • Chisel, 1/2-inch

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  1. 1

    Lay the guitar out flat on a worktable or bench. Using the tip of the utility knife, gently scrape along the length of the split. Cut loose any chips, splinters or residual debris that might be in the split.

  2. 2

    Place masking tape along both sides of the split, as close to the edge of the split as possible.

  3. 3

    Measure the length of the split with the tape measure. Mark the measurement on the spruce. Using the utility knife, peel off a strip of the spruce the length of your measurement and approximately the width of the split.

  4. 4

    Lay the strip down on the guitar. Compare the thickness and size of the strip to the split on the guitar. Lay the strip out on a flat surface and begin sanding it with the sanding block and 100-grit sandpaper to the approximate size of the split in the guitar's top. Continue sanding it by hand until it's just a bit bigger than the split in the guitar.

  5. 5

    Sand one side of the strip to a fine edge, being careful not to break the edge. Test the strip against the split. When the fine edge of the strip will fit into the split, stop sanding.

  6. 6

    Run a bead of glue along the split. Force the glue into the split with your fingertip until the split will not absorb any more glue.

  7. 7

    Align the strip with the split in the guitar. Begin tapping the strip into the split with the mallet. Work along the length of the split until the split is completely filled with the wood from the strip. Pound on the strip lightly until it breaks off and smashes into the glue in the split. Let the strip and glue dry for 24 hours.

  8. 8

    Remove the tape. Carefully scrape away any remaining bits of wood with the chisel until the surface of the guitar is flush and even where the split was.

Tips and warnings

  • If your guitar is stained a dark colour, use a stain pencil to draw on the splice, colouring it to match the colour of your guitar. If it's natural, like most acoustic guitars, the spruce should match perfectly with no touch-up.
  • Go over the spliced area lightly with rubbing compound, blending the spliced area to match the guitar's finish if desired.
  • Always wear eye protection when working with wood.

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