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SESK: Stuff Everyone Should Know · sesk.info/wood-end-grain-butt-joint

With ordinary glue, an end-grain butt joint reaches about what share of the wood's tensile strength?

Only about 25%.

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  1. About 25% ✔
  2. About 75%
  3. About 100%

Why: End grain soaks up glue like straws, leaving a starved joint, so it is a weak glue surface. Even with special techniques a butt joint reaches only about a quarter of the wood's tensile strength.

Huh, didn't know that: A scarf joint or finger joint works because it converts an end-grain joint into an edge-grain joint.

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References

Answer: About 25%. End grain soaks up glue like straws, leaving a starved joint, so it is a weak glue surface. Even with special techniques a butt joint reaches only about a quarter of the wood's tensile strength.

  1. Wood Handbook: Wood as an Engineering Material, FPL-GTR-282 (USDA Forest Products Laboratory, 2021) research.fs.usda.gov/treesearch/62200
    Even with special techniques, butt joints reach only about 25% of the tensile strength of the wood parallel-to-grain.
    Checked 2026-10-10.

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