Verleimung

Verleimung is the process of bonding wood elements with adhesives to form composite assemblies such as panels, beams, or structural members. By applying glue and pressure, individual boards or veneers are fused to increase strength, stiffness, and dimensional stability, enabling the use of low-grade or defect-prone materials. Common forms include plywood, glued laminated timber (glulam), laminated veneer lumber (LVL), and cross-laminated timber (CLT).

Process: Surfaces are prepared and dried to an appropriate moisture content. A suitable adhesive is chosen based on the intended use, including phenol-formaldehyde or resorcinol-formaldehyde for exterior or structural work; urea-formaldehyde or melamine-urea-formaldehyde for interior applications; and polyurethane or EVA for flexible or decorative bonding. The parts are spread with adhesive, assembled, and pressed under heat and pressure to cure. Quality control involves delamination tests, bond-line inspection, and moisture management.

Applications: Verleimung is used to manufacture structural timber products, such as beams and panels for buildings, flooring, and bracing, as well as furniture components and packaging materials.

Advantages and challenges: The technique enables higher strength and stiffness, efficient use of fast-grown or low-grade wood, and design flexibility. Drawbacks include moisture sensitivity, potential emissions from certain resins, required curing conditions, and higher production costs. Increasing emphasis on low-emission and bio-based binders aims to improve sustainability.

History and standards: Glue-laminated timber techniques emerged in the 20th century and have since evolved into a range of products with standardized testing and performance criteria in many jurisdictions.