# Heartwood

**The darker, denser inner wood of a tree, no longer conducting sap — the part most flooring grades are written around.**

Grades are written in terms of how much heartwood and sapwood a face may carry. NWFA/NOFMA Clear oak is described as a heartwood-dominant product allowing minimal character marks, while Select permits unlimited sound sapwood.

In black walnut the proportion is stated explicitly: No. 1 Common requires heartwood to be a minimum of 25% of the piece. Since walnut is bought almost entirely for the colour of its heartwood, the grade named on a quote materially changes what arrives.

## Related terms

- [Sapwood](https://ecowoods.ca/glossary/sapwood)
- [Flooring grade](https://ecowoods.ca/glossary/flooring-grade)


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## Provenance

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- Defined in: https://ecowoods.ca/papers/hardwood-grading-standards-nhla-nwfa#nwfa-appearance
- Citation guide: https://ecowoods.ca/ai.txt

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