ISO 8903:2016

Overview - ISO 8903:2016 (Broadleaved sawn timber - Nominal sizes)

ISO 8903:2016 defines the nominal sizes for broadleaved (hardwood) sawn timber, applying to unplaned, square‑edged and unedged boards and planks. The standard establishes agreed length, thickness and width ranges and intervals to be used in manufacturing, trading and specifying broadleaved sawn timber, and it replaces the first edition (ISO 8903:1994). Measurement and moisture‑content rules referenced in the standard ensure consistent sizing across the wood industry.

Key technical topics and requirements

• Scope: Nominal sizes for unplaned, square‑edged and unedged broadleaved sawn timber.
• Nominal lengths: From 1 m to 6 m, with size intervals of 0.1 m or 0.25 m.
• Nominal thicknesses (mm): 19 (16), 22, 27 (25), 32 (35), 40 (38), 45 (44), 50 (55), 60 (65), 70 (75), 80, 90, 100.
  • Values in parentheses are non‑preferred sizes.
• Nominal widths: Specified minimums and size intervals depending on thickness:
  • For thinner sizes (e.g., 19–40 mm): widths ≥ 60 mm, with 10 mm intervals.
  • For medium sizes (e.g., 45–70 mm): widths ≥ 80 mm, with 10 mm intervals.
  • For thicker sizes (80–100 mm): widths ≥ 100 mm, with 10 mm intervals.
• Unedged timber requirement: The narrower face must be not less than 40 mm at any point along the length.
• Moisture content basis: Nominal sizes apply to timber having an average moisture content of 20% (mlm), determined in accordance with ISO 4470.
• Measurement and vocabulary: Dimensions measured per ISO 8904; terms and definitions per ISO 24294.

Practical applications and users

ISO 8903 is used to ensure consistent sizing and clear communication throughout the timber supply chain:

• Sawmill operators and wood processors use the standard to cut and sort broadleaved sawn timber to marketable nominal sizes.
• Timber merchants, wholesalers and exporters/importers use it for product specification, packing lists and trade contracts.
• Procurement managers, architects and joiners rely on nominal sizes for project specifications and material take‑offs.
• Quality control and inspection teams use the standard in acceptance criteria and conformity checks.
• Standards bodies and regulators reference ISO 8903 for market harmonization and labeling requirements.

Related standards

• ISO 4470 - Determination of average moisture content of a lot.
• ISO 8904 - Broadleaved sawn timber - Sizes - Methods of measurement.
• ISO 24294 - Timber - Vocabulary for round and sawn timber.
• Developed by ISO/TC 218 (Timber).

Keywords: ISO 8903, broadleaved sawn timber, nominal sizes, sawn timber dimensions, timber standards, timber sizing, moisture content, ISO 4470, ISO 8904.