For most of the twentieth century, timber was treated as a traditional material: useful for furniture and for small houses, but unsuitable for the serious structural work that defined modern cities. Steel and reinforced concrete had taken over those roles, and the forests of Europe and North America, though vast, were rarely consulted when an architect needed to span a long distance or carry a heavy load. In the past twenty years, that balance has begun to shift. A series of new engineered wood products, combined with rising concern about the carbon cost of traditional materials, has pushed timber back towards the centre of structural engineering.

The key technical development is cross-laminated timber, usually known as CLT. CLT panels are made by gluing layers of solid wood at right angles to one another, much as plywood is made, but at an architectural scale. A single CLT panel may be several metres long and thick enough to serve as a floor or wall in its own right. The cross-lamination gives the panel strength in two directions, a property that ordinary solid wood cannot provide. Because the panels are machined off-site and delivered ready to install, construction on site is quiet, fast and produces little waste: a characteristic that city authorities increasingly value.

A second development is glued laminated timber, or glulam, which has actually been in use since the early twentieth century but has found new applications. Glulam beams are assembled from smaller pieces of wood, bonded end to end and side to side with waterproof adhesives. They can be manufactured in curved shapes, and they retain their strength under fire for longer than steel of equivalent load-bearing capacity. This last property surprises people, but it is well attested. When a glulam beam is exposed to fire, its outer layer chars and then protects the wood beneath. Steel, by contrast, holds its strength until the temperature reaches a critical level, at which point it softens quickly.

The environmental case for timber is also strong, though it has to be made carefully. A growing tree absorbs carbon dioxide from the atmosphere and stores it in its wood. If that wood is then used in a building, the carbon remains locked away for the life of the structure. Steel and concrete, in contrast, release large quantities of carbon dioxide during manufacture. A widely cited analysis by the Norwegian Institute of Wood Technology found that replacing a typical concrete office building with an equivalent CLT building reduces the carbon emissions associated with the structural frame by around 60 percent, provided the replacement wood comes from sustainably managed forests. Poorly managed forestry, the same analysis notes, can eliminate this benefit entirely.

These possibilities have not gone unnoticed. The Mjostarnet tower in Brumunddal, Norway, completed in 2019, stands more than 80 metres tall and is built almost entirely of engineered wood. It is not the only such project. Vienna, Vancouver and Singapore now have residential towers of ten storeys or more built around glulam and CLT. These buildings look conventional from the outside but behave differently inside: they are noticeably lighter than concrete equivalents, which allows them to be built on foundations that would otherwise be inadequate, and they absorb sound in a way that occupants describe as softer.

There are still limits. Wood, however well engineered, does not perform as well as steel in very tall buildings, where bending under wind load becomes a dominant concern. Engineer Dr. Kofi Mensah points out that timber buildings above roughly 40 storeys would require so much extra mass or bracing that the advantages over steel and concrete would disappear. Cost is also an obstacle in regions that lack local forestry industries. Importing CLT panels from Europe adds both expense and carbon, and several North American manufacturers have entered the market specifically to meet this problem.

It would be wrong to suggest that timber will replace steel and concrete in modern construction. Those materials still have indispensable roles, and for certain structures they remain superior. But the idea that wood is a traditional material, fit only for the decorative and the domestic, has been decisively rejected. In the hands of engineers working with new adhesives, new analysis tools and renewed forestry policies, timber has become what it was once, before modernist confidence took hold: a serious structural material, ready to be taken seriously again.