Laminated products

Laminated beams

Glue-laminated beams are used extensively for long spans, with smaller cross-sections laminated face-to-face with waterproof adhesives such as resorcinol formaldehyde. Pine is commonly used because of weight constraints, and because pine has a good strength/weight ratio. A built-in camber allows for long term movement of the timber so that the beam will not sag.

Plywood

Plywood is manufactured by gluing an uneven number of sheets of peeled veneer, with the grain in adjacent sheets at right angles. This gives great stability to the sheet although seasonal changes in equilibrium moisture content affect the moisture content. The reason is that cross-laying veneers compensates for the large variations in shrinkage or swelling between tangential, radial and longitudinal directions.

LVL

Laminated veneer lumber (LVL) is similar to plywood except that the peeled sheets of veneer are laid with similar grain direction. Large sheets are manufactured that are then cut to the required dimensions. The product is very uniform because any strength-reducing defects in the veneers are randomised in the laying-up.

VALWOOD

VALWOOD was an edge and face-glued product developed by Timber Technology in the late 1980s. Thin boards are easy to dry without seasoning degrade, and after dressing to 12 mm were edge-glued and allowed to come to equilibrium for three weeks. After dressing the edge-glued laminates to 10 mm, usually three were face-glued to produce a 30 mm thick panel, using urea formaldehyde fir interior use and resorcinol formaldehyde for external use. Lower quality boards can be included in the centre or back laminates. Commercial production has been low priority.