Overview
ISO 22390:2020 - Timber structures - Laminated veneer lumber (LVL) - Structural properties defines how to determine the structural performance characteristics of LVL intended for dry use (service class 1). The standard specifies methods and requirements to establish characteristic strength values (5th percentile) and stiffness characteristics (mean values) for LVL used in either edgewise (joist) or flatwise (plank) bending orientations. It does not cover formaldehyde, biological durability, fire performance, or manufacturing quality control and marking.
Key topics and technical requirements
- Scope: Applies to LVL for structural end use in dry conditions (service class 1); relevant for members in flatwise or edgewise bending.
- Characteristic values: Strength estimates are based on the 5th percentile (test durations 60–300 s); stiffness estimates are mean values.
- Mechanical properties covered: Edgewise and flatwise bending, tension parallel to grain, compression parallel and perpendicular to grain, longitudinal shear, modulus of elasticity, density, moisture content, creep and duration-of-load effects.
- Test specimen and conditioning:
- Specimens must be conditioned to equilibrium moisture at (20 ± 2) °C and (65 ± 5) % RH (constant mass criteria specified).
- If conditioning is impractical, report specimen moisture and relate to a conditioned subsample.
- Veneer and bonding requirements:
- Minimum number of veneers in cross-section: 5; maximum veneer thickness: 6 mm.
- Bonding quality shall be demonstrated per ISO 10033-1 and ISO 10033-2 using a structural adhesive suitable for dry service.
- Measurement tolerances:
- Thickness (t) and width (b): ±0.03 mm; length (L): ±2 mm.
- Cross-section angle deviation limited to 1:50 (~1.1°).
- Test setups: Bending tests use symmetric third-point loading; test span generally ≥ 18 times depth; failure modes and defects to be recorded.
Applications and who uses it
- Structural engineers and designers: use LVL characteristic strength and stiffness data for load-bearing calculations and code compliance.
- Manufacturers and product developers: develop test data for product declarations and international trade.
- Testing laboratories: implement the specified specimen preparation, conditioning and mechanical tests.
- Regulators, certification bodies and specifiers: assess conformity of LVL to international performance expectations and harmonize national standards.
- Distributors and architects: select LVL products with validated structural properties for buildings, floors, beams and prefabricated elements.
Related standards
Keywords: ISO 22390, laminated veneer lumber, LVL, structural properties, edgewise bending, flatwise bending, modulus of elasticity, 5th percentile strength, timber structures.
