ISO/DIS 22390:2026(en)

ISO/TC 165

Secretariat: SCC

Date: 2026-01-16

Timber structures — Laminated veneer lumber — Structural properties

Structures en bois — Lamibois — Propriétés structurelles

© ISO 2026

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Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents).

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www.iso.org/iso/foreword.html.

This document was prepared by Technical Committee ISO/TC 165, Timber structures.

This third edition cancels and replaces the second edition (ISO 22390:2020), which has been technically revised.

The main changes compared to the previous edition are as follows:

— the additional reference to ISO 24322 in Sections 2 and 7.4, and

— routine update of the standard.

Any feedback or questions on this document should be directed to the user’s national standards body. A complete listing of these bodies can be found at www.iso.org/members.html.

Introduction

Laminated veneer lumber (LVL) is being produced in many countries under different national standards and these products are being exported from one country to another. While the national standards have many similarities, there are also many areas of dissimilarity. Thus, there is a need for the development of this International Standard to establish consistency between these standards in order to ensure the suitability of LVL for structural end-use applications, regardless of the country of manufacture or end use. It is valuable for the industry, consumers, governments and distributors.

Timber structures — Laminated veneer lumber — Structural propertiesINTERNATIONAL STANDARD© ISO 2010 – All rights reservedISO 22390:2010(E) 63Structural propertiesTimber structures — Laminated veneer lumberStructures en bois — Lamibois — Propriétés structurellesTimber structures — Laminated veneer lumber — Structural propertiesE2010-04-12(60) PublicationISOISO  International Standard 2010ISO 22390ISO 22390ISO 22390 SCC Timber structures 165 2Heading 2Heading 1 0 CR6STD Version 2.260 4O:\Documents\TC165\050690 - ISO_CD 22390 (Ed 1)\60.00\310\050690e\C050690e.doc

This document specifies requirements for establishing the characteristic properties of structural laminated veneer lumber (LVL), including 5th percentile strength values, stiffness characteristics and other performance characteristics, related to its end use as a structural product for dry use (service class 1). It is applicable to members used in flatwise or edgewise bending orientations.

It does not cover the assessment of formaldehyde requirements, biological durability, fire performance or manufacturing, such as quality control and marking.

The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 10033‑1, Laminated Veneer Lumber (LVL) — Bonding quality — Part 1: Test methods

ISO 10033‑2, Laminated Veneer Lumber (LVL) — Bonding quality — Part 2: Requirements

ISO 13910, Timber structures — Strength graded timber — Test methods for structural properties

ISO 16572, Timber structures — Wood-based panels — Test methods for structural properties

ISO 16979, Wood-based panels — Determination of moisture content

ISO 24322, Timber structures — Methods of test for evaluation of long-term performance — Part 1: Wood-based products in bending

EN 408, Timber structures — Structural timber and glued laminated timber — Determination of some physical and mechanical properties

ASTM D143, Standard Test Methods for Small Clear Specimens of Timber

ASTM D198, Standard Test Methods of Static Tests of Lumber in Structural Sizes

ASTM D4761, Standard Test Methods for Mechanical Properties of Lumber and Wood-Base Structural Material

ASTM D5456, Standard Specification for Evaluation of Structural Composite Lumber Products

ASTM D6815, Standard Specification for Evaluation of Duration of Load and Creep Effects of Wood and Wood-Based Products

JAS 0701, Japanese Agricultural Standard for Laminated Veneer Lumber

For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https://www.iso.org/obp

— IEC Electropedia: available at https://www.electropedia.org/

3.1

laminated veneer lumber

LVL

composite of wood veneer sheet elements manufactured from one or more species, either separately or mixed, with wood fibres primarily oriented along the length of the member

Note 1 to entry: This does not exclude laminated veneer lumber with cross-laminated veneers.

3.2

characteristic value for strength

estimate of the 5th percentile values based on a statistical distribution obtained from results of tests on the defined properties with the test duration between 60 s and 300 s

Note 1 to entry: The characteristic values used for 3.2 are an estimate of the 5th percentile value of the sample as determined from ISO 12122‑1 and ISO 12122‑4.

Note 2 to entry: The defined properties are in accordance with Clauses 5 and 6.

3.3

characteristic value for stiffness

estimate of the mean property from results of tests on the defined properties with the test duration between 60 s and 300 s

Note 1 to entry: The characteristic values used for 3.3 are an estimate of the mean value of the sample as determined from ISO 12122‑1 and ISO 12122‑4.

Note 2 to entry: The defined properties are in accordance with Clauses 5 and 6.

3.4

test specimen

specimen cut from random locations within the pieces of the LVL samples

3.5

thickness

t

dimension of a cross-section, which is perpendicular to the plane of the veneers, and measured in the Y-direction

Note 1 to entry: See Figure 1.

3.6

width

b

dimension of a cross-section, which is perpendicular to the thickness (or parallel to the plane of the veneers) and measured in the X-direction

Note 1 to entry: See Figure 1.

Key

F applied load

t thickness of the LVL

b width of the LVL

Figure 1 — Cross-section of laminated veneer lumber

The minimum number of veneers in the cross-section shall be five. The maximum thickness of each veneer shall be 6 mm.

The LVL shall utilize a structural adhesive suitable for dry service (service class 1) and the bonding quality and adhesive qualification shall be determined in accordance with ISO 10033‑1 and ISO 10033‑2.

NOTE 1 Attention is drawn to national standards which can be applicable.

NOTE 2 Examples of applicable national standards include EN 314-1, ASTM D5456 and JAS 0701.

NOTE 3 Additional testing to cover more severe bonding service conditions (service classes 2 and 3) can be considered as a manufacturer's option and can be required by some national standards.

The dimensions of the test specimens shall be measured to the following accuracy:

a) for thickness (t): ±0,03 mm;

b) for width (b): ±0,03 mm;

c) for length (L): ±2 mm.

All measurements shall be made after the test pieces have been conditioned in accordance with Clause 5. Width and thickness measurements (see Figure 1) shall be the average of three measurements taken at three different positions within the middle third of the specimen. Where possible, the measurements should not be taken within 150 mm of the ends of the test piece.

Local thickness deviations related to discontinuities of the veneers, e.g., knotholes and veneer joints, are allowed, but should be avoided in the measurement of section properties.

NOTE Dimension tolerances for LVL are specified in ISO 18776.

The angle of the cross-section, α, shall not deviate by more than 1:50 (about 1,1°) from a right angle. See Figure 2, where α is the angle between the vertical axis and the sloped edge.

Figure 2 — Example of an angle, α, of a cross-section of laminated veneer lumber

Characteristic strength values for edgewise and flatwise bending, tension parallel to the grain, compression parallel to the grain, edgewise and flatwise longitudinal shear and the mean compression perpendicular to grain strength shall be determined for laminated veneer lumber, as required by the product end-use application in accordance with 3.2 and the following requirements using the test methods in this clause.

All test specimens shall be conditioned to an equilibrium moisture content resulting from a temperature of (20 ± 2) °C and a relative humidity of (65 ± 5) %. A test piece is considered to be conditioned when it attains constant mass. Constant mass is deemed to have been attained when the results of two successive weighings, carried out at intervals of not less than 6 h, do not differ by more than 1 %.

If test pieces cannot be conditioned due to their sizes, the moisture content at the time of test shall be reported and shall be within ±2 % of the moisture content of a subsample of the same product and grade conditioned in accordance with 7.2, or the provisions of ASTM D5456 may be used for developing a moisture content correlation for applications to large specimens.

If other conditions, such as tropical conditions, are used, they shall be permitted and reported. The data should be developed at the specific moisture content relative to those conditions.

NOTE Tropical interior conditions or protected exterior end use conditions may be characterized by a moisture content in the materials corresponding to a temperature regularly exceeding 30 °C and the relative humidity of the surrounding air regularly exceeding 85 % or where there is an occasional risk of wetting of the material (but excluding submerging or hosing), or prolonged exposure to weather leading to equilibrium moisture content of 18 % or higher.

For tests conducted in 5.2 to 5.8, the mode of failure and growth characteristics, such as excessive knots on the veneers and any unusual manufacturing characteristics or defects, at the failure section of each test piece shall be recorded.

The edgewise bending strength test shall be carried out using a symmetric third-point load set-up as given in ISO 13910 (see Figure 3). The test span shall be at least 18 times dimension d₂ in Figure 3. In addition, the minimum size of the specimen shall not be less than the minimum structural size manufactured.

NOTE 1 The test results can be adjusted to a common size or value based on national codes.

NOTE 2 The provisions of ASTM D5456 provide an example of a methodology to adjust for size effects.

The flatwise bending strength tests shall be carried out using a symmetric third-point load set-up as given in ISO 13910 (see Figure 3). The test span of the specimen shall be at least 18 times the depth of the cross-section (dimension d₂ in Figure 3). The minimum size of the specimen shall not be less than the minimum structural size manufactured.

Key

A and C centreline of bearing

B mid-span

d₁ width of the test specimen (t for edgewise bending and b for flatwise bending)

d₂ depth of the specimen (b for edgewise bending and t for flatwise bending)

e centrepoint deflection of the centreline of the specimen relative to the position of the centreline

  at the ends of the specimen

NOTE For illustrative purposes, Figure 3 is shown for edgewise bending only.

Figure 3 — Configuration for one third-point loading for determination of bending strength and stiffness

The tension strength tests parallel to the grain shall be carried out using gripping devices which permit as far as possible the application of a tensile load without inducing bending. The gripping devices and loading conditions actually used shall be reported. The length of the specimen between the testing machine grips shall be at least 900 mm or at least 8 times the larger cross-sectional dimension and the minimum size of the specimen shall not be less than the minimum structural size manufactured.

If the length of the specimen between the testing machine grips is different than the reference length of 900 mm, the test results may need to be adjusted to a common size or value based on national codes. A failure in the grips of the test machine invalidates the results and a new test shall be required.

NOTE The provisions of ASTM D5456 provide an example of a methodology that can be used to adjust for length effects.

The compression strength tests parallel to the grain shall be carried out such that the test piece is loaded concentrically using spherically seated loading-heads or other devices, which permit the application of a compressive load without inducing bending as given in ASTM D198. The bearing blocks and loading conditions actually used shall be reported. The length of the specimen shall be such that:

where

L is the unsupported length;

r is the least radius of gyration.

The end surfaces shall be accurately prepared to ensure that they are plane and parallel to one another and the load shall be applied in a direction generally parallel to the longitudinal axis of the test piece. The minimum size of the specimen shall not be less than the minimum structural size manufactured.

Tests used to determine edgewise shear include a centre point single span test or the double span (five-point load test) as specified in ISO 13910. When evaluating the effects of systematic manufacturing characteristics that can affect horizontal shear strength, the structural size horizontal shear test method given in ASTM D5456 or ASTM D198 may be used.

NOTE Specific test results can be different and can be adjusted according to applicable national standards.

The shear strength tests related to flatwise bending shall be carried out in accordance with the planar shear test method given in ISO 16572 or the block shear test given in ASTM D5456 or ASTM D143 or the short span bending test given in JAS 0701. The thickness of the specimen [dimension t in Figure 1 b)] shall be at least 25 mm.

NOTE Specific test results can be different and can be adjusted according to applicable national standards.

The compression strength tests perpendicular to the grain shall be carried out in accordance with the principle of ASTM D143 except that references to placement of growth rings are not applicable and the minimum specimen size is as indicated below for flatwise and edgewise orientations.

The loaded surfaces shall be accurately prepared to ensure that they are plane and parallel to each other and perpendicular to the test piece axis. The test piece shall be loaded concentrically using spherically seated loading heads and the load shall be applied at a constant rate of cross head movement throughout the test.

Depending on the product end use, compression perpendicular to grain values can be required for both the edgewise and flatwise orientations of the veneers. For flatwise orientation, the minimum cross-section of the specimen shall be 38 mm × 38 mm. For edgewise orientation, the minimum cross-section of the specimen shall be the thickness [dimension t in Figure 1a)] × 38 mm.

Local or apparent characteristic modulus of elasticity values for both flatwise and edgewise bending shall be determined. Characteristic modulus of elasticity values in tension and compression parallel to the grain shall also be determined and reported as required depending on the end-use application of the product. A correlation between axial stiffness values and bending stiffness values may be established to satisfy the determination of axial stiffness values.

The modulus of elasticity tests parallel to the grain shall be carried out in accordance with the local modulus of elasticity in the bending test method given in EN 408, using a symmetric third-point loading configuration or the apparent modulus of elasticity determined in accordance with ASTM D198 or D4761. The specimen shall be loaded in edgewise bending. The test span shall be at least 18 times the depth of the cross-section dimension d₂ in Figure 3). The minimum size of the specimen shall not be less than the minimum structural size manufactured.

This value may be determined in combination with the test in 5.2.

Dynamic vibration methods to determine edgewise modulus of elasticity may be used, provided they have been calibrated to static methods.

The modulus of elasticity tests parallel to the grain shall be carried out in accordance with the local modulus of elasticity in the bending test method given in EN 408 using a symmetric third-point loading configuration or the apparent modulus of elasticity determined in accordance with ASTM D198 or ASTM D4761. The specimen shall be loaded in flatwise bending. In flatwise bending, the depth of the specimen [dimension d₂ in Figure 3)] shall be the full thickness of the slab from which it was manufactured [dimension t in Figure 1 b)] and the test span shall be at least 18 times d₂ in Figure 3. The minimum size of the specimen shall not be less than the minimum structural size manufactured.

This value may be determined in combination with the test in 5.3.

Dynamic vibration methods to determine flatwise modulus of elasticity may be used, provided they have been calibrated to static methods.

The test pieces shall be of full cross-section with a minimum length to provide a test length between the testing machine grips of at least 8 times the larger cross-section using self-aligning grips (see 5.4). The tension load shall be applied without inducing bending in the specimen. The maximum load applied shall not exceed the proportional limit load or cause damage to the test piece. Deformation shall be measured over a gauge length greater than five times the larger cross-sectional dimension of the piece and located no closer to the grips than twice the larger cross-sectional dimension.

The test pieces shall be of full cross-section with a minimum length of six times the smaller cross-sectional dimension in accordance with EN 408. The maximum length shall be such that:

where

L is the unsupported length;

r is the least radius of gyration.

The test pieces shall be loaded concentrically using spherically seated loading heads, such that the compressive load is applied without inducing bending. Deformation shall be measured over a gauge length of four times the smaller cross-sectional dimension of the piece. Extensometers should be positioned on opposing faces or corners to compensate for end rotation during loading.

Fifth percentile as well as mean characteristic density values shall be determined, as required by national standards.

The density shall be determined in accordance with the method given in ISO 13910.

The moisture content shall be determined in accordance with ISO 16979, EN 322 or ASTM D4442.

Species equivalency shall be determined between the laminated veneer lumber and a species or species combination of sawn timber for purposes of establishing withdrawal capacities of nails and bearing capacities of dowel-type fasteners. Species equivalency shall be established by determining an equivalent specific gravity for the laminated veneer lumber using the procedures of ASTM D5456.

Creep and duration of load (DOL) performance of the LVL shall be evaluated in accordance with Section 10 of ISO 22390, ASTM D6815 or equivalent for dry conditions of use. LVL products that meet the requirements of Section 10 of ISO 22390 or ASTM D6815 shall be permitted to use the creep and DOL factors applicable to sawn lumber. At a minimum, one representative grade (containing veneer joints at the expected frequency and spacing anticipated in production) per adhesive being used shall be evaluated. For products manufactured with one or more species, either separately or mixed, the greatest anticipated percentages of the highest density species should be evaluated. Hardwood and softwood species shall be evaluated separately. At a minimum, this test should be performed in the primary orientation intended for the end use of the product, that is, edgewise, flatwise or both.

NOTE This test is only applicable to bending stresses and is not intended to be used for determining performance in axial tension or axial compression.

Bibliography

[1] ISO 12122‑1, Timber structures — Determination of characteristic values — Part 1: Basic requirements

[2] ISO 12122‑4, Timber structures — Determination of characteristic values — Part 4: Engineered wood products

[3] ISO 18776, Laminated veneer lumber (LVL) — Specifications

[4] EN 314‑1, Plywood — Bonding quality — Part 1: Test methods

[5] EN 322, Wood-based panels — Determination of moisture content

[6] ASTM D4442, Standard Test Methods for Direct Moisture Content Measurement of Wood and Wood-Base Materials