Structural glued laminated timber

Glued laminated timber

Glued laminated timber (glulam) is manufactured from at least three bonded lamellae with parallel fibre orientation. The timber is kiln dried, planed, and classified into strength classes by visual or machine grading.  The suitability of the wood species in glulam construction has to be demonstrated. Spruce, pine, and larch are most commonly used. Straight as well as curved beams can be manufactured. One can distinguish between homogenous (all lamellae across a beam's cross-section belong to one strength class) and combined (outer and inner lamellae belong to different strength classes) glued laminated timber. Glued laminated timber is particularly suitable for components bearing high stresses or spanning large distances that have to satisfy stringent requirements with respect to dimensional stability and appearance.

Solid wood panels

In solid wood panels, individual hardwood and 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. 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. No open joints are allowed in the core layer.

Finger-jointed solid construction timber

Finger-jointed solid construction timber is graded, kiln-dried, and planed solid timber, which can be manufactured in nearly any length. Finger-jointed solid construction timber is classified into strength classes by visual or machine grading. Different strength classes apply to softwood and hardwood timber.  This standard defines the performance requirements and also sets a maximum wood moisture content of 18%. The natural durability against a biological attack on this type of timber product depends on the wood species used. The durability can be enhanced with standard techniques such as preventative biocides.

Laminates

Cross laminated timber (CLT) consists of at least three layers of layer-glued (or joined using dowels) softwood timber planks where the direction of the grain in the adjacent layers is perpendicular to each other. Individual planks are either visually sorted or machine graded prior to joining using adhesives or dowels. Lay-up of CLT has to be symmetrical in the 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 cross laminated timber (in the latter, the dimensions of individual elements are larger)