Glulam

glulam constructed single-storey extension

Glued laminated timber, or Glulam as it is more commonly known, is an engineered wood product. Glulam technology was developed in Germany at the end of the nineteenth century and the world’s oldest glulam factory, Töreboda in Sweden is still in use today. Glulam has many applications: schools, sports halls, railway stations, industrial, agricultural and commercial buildings, shopping centres, bridges and even homes.

Glulam is manufactured from layers of parallel timber laminations, normally Spruce or Pine. For applications requiring more durability, the options are Larch, Douglas Fir, Oak and Sweet Chestnut. In order to fabricate Glulam, laminates of timber are arranged with their grain parallel to the longitudinal axis of the member. This method of construction ensures that any timber weaknesses, such as knots or splits, are equally spread through the individual laminates. This is an advantage over a solid timber element from the same species.

Performance
Glulam has greater strength and stiffness than structural timber of similar dimensions. Glulam also has a better strength to weight ratio than steel. This means that glulam beams can span large distances with a minimal need of intermediate supports.

The longer lengths of glulam are fabricated by finger-jointing the laminates and then gluing them together. This process forms a member which functions as a single structural unit. The resultant high load-bearing capabilities and dimensional stability means that Glulam can be manufactured up to 50 metres long. In addition to straight prismatic sections, beams can be single-tapered, double-tapered and bevelled.

Glulam is a flexible construction material, lending itself very well to curved forms, such as arches, frames etc. The shaped Glulam is manufactured by bending laminates on formers. These are then bonded together with adhesive, clamped and then cured. The resulting profiles could be anything from a simple curved beam to a pitched and tapered curved beam. Even complex arch configurations are possible.

Structural design
Portal frames can have curved or finger-jointed haunches. Glulam beams can be arranged in the form of a grid. Shell structures provide a wide choice of advanced forms free from columns. There are also many complex structural systems, e.g. arch and beam frame. One advantage is that all glulam components can be made in the factory in suitable sections for transportation, and then assembled on the building site. and partly because its strength is particularly favourable for large spans. Free spans of over 100 m have been built.

Assembly
Glulam structures can be erected quickly and simply by using prefabricated units. The parts are assembled by nailing, screwing or bolting, unaffected by the time of the year or the weather, and any adjustments can be made with simple hand tools. A glulam frame can carry its full load immediately after the assembly. It is a well tested building material which, correctly used, has extremely good durability.