Wooden, sustainable, and increasingly tall!

Constructions relying on Cross-Laminated Timber technology rival concrete and steel architectural solutions.

12 September 2022

Pulpwood in a stack in a coniferous forest

By Mariusz Bogacki, Researcher and Science Communicator, Edinburgh

For centuries, timber was one of the most common materials used to build structures. Following many city fires in the 19th century, the material came to be seen as unsafe, and steel and concrete replaced wood as a more secure and durable source of construction material. However, with the help of Cross-Laminated Timber (CLT) technology, wooden structures are making a comeback!

Of the many types of structural timber, also known as mass timber, Cross-Laminated Timber (CLT) has proven to be the most promising one. Construction of CLT involves sticking and cross-stacking together solid-sawn lumber. The final product are large timber slabs (up to a foot thick and 18-feet long by 98-feet-wide) that can be used as building blocks, walls, and floors of structures, such as houses or even skyscrapers. You can think of it as massive wooden Lego blocks!

There are many benefits to CLT. Timber is a naturally renewable source of material. CLT is not only produced at lower costs than traditional steel or concrete materials, but it also allows for faster and less wasteful construction. In fact, according to some lifecycle analysis, CLT should be considered as carbon-neutral (as long as the wood comes from a sustainably managed forest). Switching to CLT and other timber related constructions would therefore contribute to decarbonising the building sector. Finally, no, CLT is not as flammable as you might think! Large, solid, and compressed masses of wood are actually quite difficult to ignite and, because of their density, retain their structural integrity for many hours even when subjected to intense fire.

CLT was originally developed in Austria in the early 1990s. However, perhaps it is not surprising that the Nordic countries, with their well-managed forestry, are leading the way these days. The world’s tallest timber structure – 18 stories and over 280 feet – is in Norway. Sweden’s tallest timber building might only be 8.5-stories tall but it’s part of a larger drive to build more sustainable housing complexes across the country. Other cities around the world are also catching on the trend. The Netherlands has its own 21-stories tall timber tower, and the city of Chicago has recently proposed an 80-stories wooden tower.

As the technology develops, we might see more taller wooden structures in global metropolises. Environmental benefits, coupled with appealing aesthetics and modernist feel are promising to drive this trend further – and higher!