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Cross Laminated Timber (CLT)

CLT consists of at least three layers of layer-glued (or joined using dowels) softwood timber planks where the direction of the grain in adjacent layers is perpendicular to each other. Individual planks are either visually sorted or machine graded. Lay-up of CLT has to be symmetrical in cross section of the product. Planks may be joined by edge-gluing and may also be finger-jointed in the longitudinal direction. There is a gradual transition from multi-layered solid wood panels to CLT (larger dimension of individual elements).

Solid wood panel

In solid wood panels, individual softwood lamellae are sorted, planed, and assembled into multi-layered boards consisting of parallel outer layers and at least one core layer perpendicular to the orientation of the outer layers. Adhesive is used to bond the lamellae. Thus swelling and shrinkage due to climatic changes is minimal. Solid wood panels have a symmetric lay-up and the thickness of the outer layers is recommended to be at least 5 mm to fulfil the requirements for loadbearing structural timber components. No open joints are allowed in the core layer.




Plywood consists of at least three veneer layers glued together crosswise. Therefore the layers are placed adjacent to each other and at right angles. The lay-up of boards has to be symmetrical throughout the board thickness. The single veneer layers are manufactured by peeling steamed roundwood. The thickness of individual veneers must not exceed 7 mm. Boards for applications in dry, humid or exterior conditions are available.

Laminated Veneer Lumber (LVL)

LVL is used as panel- or beam product. It consists of peeled spruce or pine veneers up to 6 mm thick. These wood veneers are bonded with their individual ends offset and with fibres oriented primarily in the same direction. LVL is manufactured in a continuous process, using a phenolic resin. LVL contains veneers with fibres aligned primarily in the major axis, sometimes veneers also align with the minor axis. LVL can be used as bracing element in load-bearing floors and ceilings. LVL containing veneers with fibres aligned exclusively in the major axis is used in load-bearing structures, trusses, beams and rafters. LVL can be used in the same applications as glued laminated timber. LVL is suited for pressure treatments and thus can be designed for special applications, such as in areas with high risk to biological attack (e.g. by fungi or insects) or where special climatic conditions prevail.