Developed in Europe in the 1990s, X-LAM (or CLT) transformed timber from a linear element (beam or column) into an isotropic planar material, equivalent to a prestressed concrete slab but at a fraction of its weight.
The production process eliminates the natural defects of timber. The boards are kiln-dried to 12% moisture, scanned to remove loose knots, planed and finger-jointed. They are then arranged in superimposed layers crossed at 90 degrees in an odd number (3, 5 or 7), glued at very high pressure with polyurethane or melamine resins.
Despite popular belief, X-LAM has excellent fire behaviour. Wood burns at a constant and predictable rate (charring rate about 0.65 mm/min); the outer charred layer acts as a thermal insulator, protecting the structural core far longer than bare steel. In seismic zones, the stiffness of the panels combined with the high ductility of the mechanical joints ensures excellent dissipation of seismic energy.
Standards
European and international references applicable.
Physical properties
Usage environment
Designed for Service Class 1 and 2 only (covered structures). Ground contact must always be kept clear of foundations to prevent capillary-rise rot.