Why timber? Because it grows on trees

The broad tiers of the pagoda at Hōryū-ji temple in Nara Prefecture, Japan, tower five storeys high. At least 1,300 years old, eleven structures on the temple site have withstood the violent earthquakes that have shaken these islands dozens of times in the past millennium or so – not to mention outlasting weather and decay.

Creating tall and spectacular buildings from wood is nothing new, but in the meantime other materials have come to dominate. On a planet where building materials account for around 11% of global greenhouse gas emissions, wood has the potential to revolutionise the carbon footprint of construction. Not only does the material by-pass the energy-intensive processes that concrete and steel require, it locks up carbon for the lifetime of the building.

“Timber is one of the few truly renewable building materials,” explains Brent Cross Town’s development director Peter Runacres. Wooden buildings are also much easier to adapt if you need to. “Who knows what the future of the workplace will be like in five, ten or twenty years’ time? We want to create buildings that are there for a long time and are supremely adaptable… It’s much easier to do that with a timber building that you can cut and carve.”

Today’s cutting-edge timber buildings aren’t made of a wood that Neolithic architects would recognise. Engineering breakthroughs mean that timber can now match the performance of steel and concrete, opening up possibilities for taller buildings and raising wood’s status from cabins to construction at scale. The secret is a product known as cross-laminated timber (CLT), a material we’re exploring at Brent Cross Town.

CLT uses layers of wooden boards glued together in a cross-hatch pattern, like you would arrange a game of Jenga. Several layers thick, the boards are pressed and precision-cut into panels of exactly the right size. About as strong as steel and concrete, the panels are up to 80% lighter. Their structure means that they pass muster on fire safety: the outer layers char predictably and protect the inner layers from oxygen – providing better results than steel, which plasticises (melts) suddenly when it reaches a high enough temperature. Wood even has that little bit of give to it that allowed the Hōryū-ji temple the ductility to survive earthquakes for over a thousand years. 

Best of all, wood is an all-round sensory delight, from that hint of forest smell to the mellow acoustics to the tactile grain. “It’s proven to increase productivity, it’s proven to make people less stressed because they feel like they’re in a more natural environment,” says Runacres, “There’s no VOCs being given off, there’s no strange off-gassing from manmade materials that we tend to put in. It’s a much more natural and healthy environment and that is greatly underplayed.”

For our office buildings at Brent Cross Town, we’re looking at designs that are constructed either entirely out of timber or from a combination of timber and low-carbon concrete. Runacres says, “To lease buildings you know are going to make the occupants better and healthier – well, what a fantastic place to be as a developer.” You just have to be careful not to go Scandi-mad and make everything look like a giant sauna, he jokes.

As we build this North London neighbourhood, we’re undertaking a lifecycle analysis for each and every plot that will tell us its carbon footprint. Where we can, we’ll use timber and other low-carbon materials. Where we can’t, we’ll offset the emissions through certified schemes.

Environmental groups have pointed out that wood is no silver bullet for climate-friendly construction. For a start, it’s essential that forests are sustainably managed. And it would be simplistic to say that using timber always removes carbon from the atmosphere, given that shipping and processing the material still expends energy. As we pledge to build a zero net carbon town here at Brent Cross Town, we’re all too aware that this is a complex and challenging journey. But wood has incredible potential to change the way we build and live for the better. The natural world supplies every fundamental need, meaning the answers to some of humanity’s most serious problems really do grow on trees.