ISO 12122-2:2014

Overview

ISO 12122-2:2014 - "Timber structures - Determination of characteristic values - Part 2: Sawn timber" - defines statistical and procedural methods for deriving characteristic values from test results for a defined population of sawn structural timber. Intended to be used alongside ISO 12122-1, this part covers both mean-based and 5th percentile–based characteristic values and specifies how sampling, conditioning and test data are managed so characteristic properties accurately represent the reference population.

Key topics and requirements

• Scope and linkage
  • Applies to structural sawn timber; read together with ISO 12122-1 for basic requirements.
• Reference population
  • Requires a clear definition of the reference population; attributes to declare include climate, altitude, silviculture, soil type, sawing pattern, seasoning method and grading/production method.
• Sampling
  • Sampling method must represent population variants; sample size should reflect the expected coefficient of variation (V) - sawn timber typically needs larger samples due to higher variability.
• Sample conditioning
  • Storage and test environment must match the reference population conditioning (e.g., moisture content, seasoning).
• Test data and methods
  • Test results should be obtained using ISO 13910 or an equivalent method with validated equivalency factors.
  • Adjustments (size, moisture, pooling data) must follow ISO 12122-1 and be documented.
• Evaluation of characteristic values
  • Modulus of elasticity (MoE): characteristic MoE for serviceability is the sample mean; for ultimate limit state it may be the mean or the 5th percentile depending on design approach.
  • Strength values: bearing strengths (parallel and perpendicular to grain) are taken as mean properties; other strength properties use the 75% lower one-sided confidence limit on the test 5th percentile (methods defined in ISO 12122-1).
• Reporting
  • Reports must comply with ISO 12122-1, documenting population definition, sampling, conditioning, test methods and all adjustments.

Applications and who uses it

• Structural engineers and designers using sawn timber in buildings and infrastructure to establish reliable material property values for design or to derive design values.
• Timber manufacturers, graders and producers who need to demonstrate product characteristics for grading, certification, or market claims.
• Testing laboratories that perform mechanical property tests and report characteristic values in accordance with international practice.
• Standards bodies and code committees deriving or harmonizing design values and safety margins for timber structures.

Related standards

• ISO 12122-1 - Basic requirements for determination of characteristic values (mandatory companion document).
• ISO 13910 - Specified test methods for sawn timber (or equivalent test methods with validated equivalence).

Keywords: ISO 12122-2:2014, sawn timber, characteristic values, timber structures, modulus of elasticity, 5th percentile, sampling, ISO 13910, structural timber.