"The rise of mass timber is a quiet revolution" says Clare Farrow
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"If urban densification is inevitable, then let it be done with a material that makes us happy"

The mass-timber revolution is coming, says Clare Farrow, co-curator of the new London exhibition Timber Rising: Vertical Visions for the Cities of Tomorrow.


Revolution is in the air. In this year of centenaries – remembering the end of the Russian Revolution and the success of the British suffrage movement in getting votes for women in 1918 – the world of architecture, engineering and construction is experiencing its own, quieter form of revolution: the rise of mass timber as an alternative to the dominance of concrete and steel.

It is a challenge to the status quo, a desire to improve urban lives and the environment too, and a recognition that something urgently has to change. Perhaps surprisingly for a revolution, the material chosen is the most ancient one of all.

Urban densification is both a reality and a necessity. By 2050, the world's population is projected to reach 9.8 billion, with around 70 per cent of people living in cities, and increasing numbers experiencing poverty and inequality.

It seems that the only choice is to build upwards

As urban areas become more densely occupied and land prices soar, it seems that the only choice is to build upwards. New luxury towers built of concrete, steel and glass present exciting and symbolic visions of this future, a penetration of the clouds. But there is also a flip-side.

The problem is that cities already account for 75 per cent of global pollution and consumption of non-renewable resources. In the UK for example, the energy consumed in the construction and operation of the built environment accounts for almost half of the country's carbon dioxide emissions.

In addition to the statistics are the realities of human nature and psychology: tower blocks are often associated with poverty, social problems, dangers and isolation, more so now than ever following the tragedy and scandal of Grenfell Tower. People innately fear a loss of privacy, individuality, and contact with nature, and equally the prospect of being forced out of cities as the cost of buying or renting becomes more and more inaccessible.

Tower blocks are often associated with poverty, social problems, dangers and isolation

In this context, it may seem extraordinary to be proposing a material that was itself rejected in the modern age, precisely because of fear and prejudice. Disasters such as the 1871 Great Fire of Chicago changed the perception of wood overnight, paving the way for the rise of industrial materials and the first skyscrapers; Stalin ordered the destruction of wooden housing, which the Bolsheviks associated with a Tsarist past; and in Japan, the horrors of the second world war meant that building wooden structures in densely packed urban areas was unthinkable. Only towards the end of the 20th century did perceptions begin to change, and architects again start to explore the potential of wood.

Experiments with engineered timber, including cross-laminated timber (CLT) and glue-laminated timber (glulam), were initially driven by reports on climate change and the understanding that wood can absorb and store carbon dioxide to an almost magical degree.

Convinced that large-scale CLT panels – assembled according to the principles of plywood, using timber from responsibly managed forests – could be structurally sound and safe at height, a small number of architects, scientists and engineers began to push the possibilities of this new material. In doing so, they discovered that timber has more to offer than its carbon credentials alone.

Timber has more to offer than its carbon credentials alone

Wood has a combination of lightness and tensile strength that nature excels at mastering. It is five times lighter than concrete, and yet it has comparable strength-per-weight ratio. This lightness – combined with wood's thermal performance, and the fact that the vast panels retain the natural grain and even scent that is so familiar to us – has led architects and engineers to consider how mass timber might be used for urban densification.

While the press has largely focused on the almost dream-like concept of wooden skyscrapers – put forward in scientifically-backed research and competition proposals such as Baobab, for Paris, by Michael Green Architecture, and PLP Architecture's concept for a timber skyscraper at London's Barbican. Intentionally "provocative", according to the architects, these proposals are designed to test public and media response, however, the timber debate is much more far-reaching than a simple competition for height.

Press has largely focused on the almost dream-like concept of wooden skyscrapers

Because of the material's lightness – Kevin Flanagan of PLP likens CLT to the carbon fibre used in aeroplane wings – mass timber can be used to build on top of other structures. This opens up all kinds of exciting, vertical-layering possibilities by adding density to existing buildings instead of requiring new land.

Moreover, its lightness means that neglected brownfield sites, over old Victorian sewers for example, can be considered as land for vertical housing. Waugh Thistleton Architects demonstrated this at Dalston Lane, in London. Built from CLT, the building could rise taller than was ever thought feasible due to the lightness of timber in comparison to concrete.

In fact, Andrew Waugh's argument is that we don't necessarily need to be thinking of wooden skyscrapers in London, however seductive the concept is, but rather of increasing density across the board. He is thinking more in terms of 10-15 storey buildings, which many believe to be the comfortable height for human beings. What is needed, he argues, is a broader political understanding of the potential of engineered timber.

Timber towers can also be ingeniously inserted into awkward, narrow urban spaces that are impossible for other materials. PLP Architecture explored this idea in a proposal called Timber Tower 2 in the Netherlands, and in doing so evolved a new type of load-bearing structure inspired by basket weave, unlike anything that could be built in concrete and steel.

It's still very early days for CLT, and other forms of engineered timber, in spite of their ancient origins

This is the point that timber advocates such as TED speaker Michael Green are making: it's still very early days for CLT and other forms of engineered timber, in spite of their ancient origins. The material itself will soon drive new, revolutionary types of architecture, aided by the accuracy of prefabrication methods and the consequent speed and lack of waste of on-site construction.

The process is quiet, fast and non-toxic, as Waugh describes, "the people who are working on site are in these environments that are pine-scented, not toxic, and the productivity and happiness we see is remarkable. We need to rethink the way we build, in terms of architecture and construction."

Waugh, who lives in a CLT house himself, is also persuasive about the benefits to residents' health, which will have huge implications for urban densification, given the urgent concerns about mental health in cities, its impact on the economy, and the possibility of this worsening.

"It's a beautiful environment to live in. It's calmer, more serene, and you sleep better. Our house is never hot and never cold. It feels like it shapes itself around you. It feels organic," he says.

Studies are showing that the presence, scent and touch of wood can have remarkably positive effects, not only on people's wellbeing in a general sense, but more specifically on stress levels, blood pressure, communication, learning and healing.

The presence, scent and touch of wood can have remarkably positive effects

It makes perfect sense, especially when timber towers incorporate balconies and planting systems, that a sense of alienation in vertical living becomes less of an issue when a contact with nature and its materials are maintained. As Japanese architect Kengo Kuma recently said, "wood is my friend".

In the first half of the 20th century, Alvar Aalto, who brought a warmth of touch to Modernism, commented that wood is "a form-inspiring, deeply human material". If urban densification is inevitable, then let it be done with a material that makes us intuitively happy, as well as benefitting the planet and specifically the air, which after all, we share with trees.