Overview
ISO 12122-4:2017 - Timber structures - Determination of characteristic values - Part 4: Engineered wood products defines methods to derive characteristic values for engineered wood products (EWP) from test results. Intended to be used together with ISO 12122-1, this part specifies how to determine characteristic material and component properties (e.g., modulus of elasticity, shear modulus, bearing strength, component stiffness or capacity) for a defined reference population of products such as plywood, OSB, I-beams, LVL and structural insulated panels.
Key topics and requirements
- Reference population: Describe the population attributes (raw material sources, adhesive type and curing, grading/production, quality control, secondary processing and product configuration) so samples represent the production population.
- Sampling and sample size: Sampling must follow the performance objective in ISO 12122-1 and reflect variant proportions in the reference population. EWPs typically have lower coefficient of variation, which can affect required sample size.
- Sample conditioning: Test and storage environments must match the conditioning defined for the reference population.
- Test data: Use relevant ISO product/test standards or equivalent methods with established equivalency factors. Record failure modes and include only tests producing the appropriate failure mode for the property evaluated.
- Evaluation methods:
- Material properties: Characteristic modulus of elasticity and shear modulus are taken as the mean of test values. Bearing strength (parallel and perpendicular to grain) is reported as mean values.
- Component properties: Characteristic stiffness is the mean of test values; bearing strengths follow material-property rules.
- 5th percentile-based properties: For strength-related properties, evaluate the test 5th percentile and the 75% lower single-sided confidence limit, using methods in ISO 12122-1.
- Reporting: Reports shall comply with ISO 12122-1 requirements and include sampling, conditioning and test method details.
Applications
- Establishing characteristic mechanical properties for product certification, type approval, or CE marking.
- Informing structural design inputs where EWP properties are required for capacity or stiffness calculations.
- Supporting product development and quality assurance programs by quantifying population-level properties.
- Providing data for conversion of characteristic values into design values (when combined with appropriate safety factors).
Who should use this standard
- Timber product manufacturers and test laboratories
- Structural engineers and designers working with engineered wood
- Certification bodies, regulators and standards committees
- R&D teams developing or validating engineered wood products
Related standards
Keywords: ISO 12122-4:2017, engineered wood products, characteristic values, timber structures, modulus of elasticity, bearing strength, sampling, sample conditioning, 5th percentile.