Glulam Long-Span Structures

Glulam exists for a precise reason: it delivers members of a size and length no tree can provide, with more reliable strength than solid timber because defects are spread among the laminations instead of concentrating at one point. This is what makes it the material of long spans: sports halls, swimming pools, industrial sheds, stadium roofs. The operational consequence is that the site changes nature. You do not build: you assemble. Members arrive finished, with holes already drilled and plates already fitted, and the work on site is positioning, aligning and tightening. This means the decisive phase is not erection but the detailed design of the connections, the moment when it is decided how forces pass from one member to another. A notch cut on site to run a pipe can drastically reduce a beam's capacity, because it severs the fibres exactly where they work hardest. The second theme is water, and not only rain. Glulam fears moisture more than anything else, and the most vulnerable point is the beam end: end grain absorbs by capillarity far faster than the side face. This is why a bearing that lets water pond under the beam end is the worst defect you can leave, and why members must be protected in transport and storage, not only once the building is complete. Finally there is fire, where timber behaves better than its reputation. Burning, it forms a charred layer that protects the core, and the rate at which the front advances is known and predictable: the section is sized so that after the required period enough sound timber remains to carry the load. It is the opposite of steel, which does not burn but loses strength quickly and must be protected.

This is where timber suffers the most stubborn prejudice, and reality is almost the opposite of intuition. Timber burns, certainly, but in burning it forms a charred surface layer that is a very poor conductor: that char insulates the core and slows the advance of the front, which proceeds at a slow, measurable and known rate. The result is that a large section loses a few centimetres per face but keeps a sound core that goes on carrying, and does so predictably: the beam is sized so that after the required fire resistance period enough sound material remains. Steel, by contrast, does not burn at all, but it is an excellent conductor: it heats quickly throughout the section and towards fire temperatures loses most of its strength, failing with little warning. This is why steel must be protected with intumescent paint or boards, while the exposed glulam of a sports hall often needs nothing at all.

It is the biggest cultural difference between glulam and traditional techniques, and anyone coming from concrete or masonry underestimates it systematically. In a pour or in masonry the site has room: you adapt, add and correct as you build. In glulam you do not. The member arrives glued, shaped, drilled and treated, and every later modification is a subtraction of strength, because it cuts fibres that were continuous. This shifts the centre of gravity of the work upstream, into a phase where there is still nothing to see: coordination between structural engineer, services engineer and architect must close before the order, and changes after that moment cost as much as a new member and its weeks of production. The reward, in exchange, is extremely fast and clean erection: a roof that other techniques would take months to close is finished in days, with no water on site and very little waste.