EN 15425:2023+A1:2026

Overview

EN 15425:2023+A1:2026 is a European standard developed by CEN that specifies the classification and performance requirements for one component polyurethane (PUR) adhesives used in load-bearing timber structures. This standard supports manufacturers, quality assessors, and stakeholders in the timber construction industry by establishing clear guidelines for adhesive selection based on defined climatic exposure conditions and specific applications within factory or factory-like manufacturing environments.

The standard also addresses the classification of "adhesive product lines," where all products within the line share the same chemical composition except for varying catalyst amounts. Importantly, EN 15425:2023+A1:2026 focuses solely on the performance of adhesives under controlled conditions, specifically excluding site applications and the manufacture of most wood-based panels apart from solid wood panels.

Key Topics

• Classification of PUR Adhesives
  EN 15425 introduces a systematic classification based on:
  • Service class suitability (indoor, covered exterior, or full exterior exposure)
  • Maximum test temperature (50°C, 70°C, 90°C)
  • Maximum permissible glue line thickness and application area (finger-jointing, general, or special purpose)
• Performance Requirements
  • Mechanical strength criteria, such as minimum tensile shear strength after specified climatic treatments
  • Limits on delamination for bonded timber under thermal and moisture stresses
  • Requirements for resistance to acid damage, static and dynamic loading, and the effects of wood shrinkage
  • Long-term performance under cyclic climate conditions (creep and load tests)
• Scope and Limitations
  • Applies exclusively to adhesives for factory manufacturing, not for on-site or off-site assembly
  • Does not cover use in modified or stabilized wood (e.g., acetylated, heat-treated, or polymer-impregnated timber)
  • Excludes adhesives combined with direct water-spraying during the bonding process, though informative guidance is available in Annex C

Applications

• Timber Manufacturing and Construction

  • Critical for producers of glued laminated timber, solid wood panels, and engineered wood products requiring factory-controlled bonding processes
  • Helps ensure the long-term performance of structural timber elements in environments ranging from interior (service class 1) to severe exterior (service class 3) conditions

• Quality Assurance and Compliance

  • Offers a framework for type testing and quality assessment of PUR adhesives before their use in load-bearing timber structures
  • Used by manufacturers to demonstrate product conformity and support safe, durable construction practices
  • Forms the basis for product certification and helps meet regulatory and contractual demands within European and international timber markets

• Product Development

  • Guides adhesive manufacturers in designing and documenting product lines to meet varying service requirements and environmental exposures
  • Supports innovation and optimized adhesive performance targeting specific timber species and factory processes

Related Standards

EN 15425:2023+A1:2026 cites and complements a series of European and international standards addressing adhesives for load-bearing timber structures, including:

• EN 302 series: Test methods for evaluating adhesive performance (tensile shear strength, delamination resistance, acid/humidity cycling, etc.)
• EN 14080: Requirements for glued laminated timber and glued solid timber
• EN 15416 series: Additional test methods for climatic load and creep testing
• EN ISO 2555: Determination of viscosity for resins and adhesives
• EN 923: General terms and definitions for adhesives

Adherence to EN 15425 ensures that adhesives meet rigorous standards for mechanical performance and durability, supporting the reliability and safety of load-bearing timber construction across diverse European climates.