True or false: Wood is not a suitable material for industrial construction

Is wood a fire-safe construction material?

Contrary to popular belief, wooden structures are extremely load-bearing in the event of fire. Wood has low thermal conductivity. Also, the char layer forms on the outside of the material, protecting the wood core from burning through and collapsing.

Fire safety regulations vary from country to country. There are different restrictions for the number of storeys and the height of wooden buildings, as well as requirements for safety equipment, mainly sprinklers. Industry professionals have called for harmonising the regulations in order to create standardised structures and processes for taller wooden buildings.

How about the other possible limitations wood has as a construction material? 

Wood is a natural, living material that has natural, living features. Wood shrinks and swells, especially in the tangential direction. This fact needs to be taken into consideration when designing building frames. Strength-graded sawn timber that is dry enough for construction shrinks 0.8 percent in the tangential direction and 0.2 percent in the vertical direction.

Then again, the mechanical behaviour of wood is very well known throughout the industry and among designers. With strength-graded sawn timber, it is reasonable to build a four-storey building. But, with laminated veneer lumber (LVL) or cross-laminated timber (CLT), even eight storeys is not a problem – solid wood can carry heavy loads with minimal weight. The strength-to-weight ratio of wood is excellent compared to other building materials.

What other advantages does wood offer for industrial construction?

In the building frame and surfaces, one of the most significant benefits of wood is that it is hygroscopic: the cellulose cell structure absorbs and dissipates humidity. Unlike steel, plastic, concrete, or glass wool, wood does not cause condensation points that can lead to water damage or mould growth.

Another benefit of wood is its porosity. It does not cause thermal bridges in the same way as concrete or steel. In windows, a softwood window frame provides a thousand times as much insulation as an aluminium equivalent and nearly 400 times as much as plain steel.

In an industry that is one of the key contributors to greenhouse-gas emissions, the main advantage of timber is its relatively low carbon footprint. When growing, one cubic metre of wood binds approximately 1,000 kilos of carbon dioxide and releases 700 kilos of oxygen. In buildings, wood retains this beneficial effect by acting as a carbon storage. Manufacturing wooden products is also energy-efficient. It takes only one-sixth of the energy to produce a laminated wooden beam compared to a steel one of comparable strength.

For the European Union to meet its climate targets, new buildings need to be carbon-neutral by 2030. Carbon accounting will become compulsory for the construction industry in 2026. This will undoubtedly increase the use of wood.

It feels compelling to compare the features of different construction materials. However, the combination of different materials might create the best end result. “I believe that the juxtaposition between concrete and wood is over. We will see a rise of hybrid construction,” Markku Karjalainen says.

Sustainability Manager Jaakko Paloheimo from UPM Plywood also contributed for this article.