Height isn’t everything

Alex de Rijke of dRMM says that while architects are exploiting the possibilities of timber to build tall, this should not reinforce a view of towers as the answer to urban density, and it’s unrealistic to expect them to be true timber buildings

Why do architects want to build high – specially in timber? Like testosterone-fuelled explorers driven to go further, the challenge is apparently irresistible. The biggest erection wins the global reputation, the research stakes, the media interest, the TED talk and the necessarily short-lived title of the ‘World’s Tallest Timber Tower’.

At dRMM Architects we pioneered engineered timber architecture in the EU, exhibiting the first cross-laminated flatpack prototype house in Oslo in 2006, and realising state school buildings from 2007. In 2009 the practice proposed a 6000 seat Handball Arena for the 2012 London Olympics, and a 10 storey all-timber apartment building design to developer Lend Lease for the Athlete’s Village. This, also ahead of its time, was in the event built in concrete frame, but LendLease went on to build the 10-storey Forte CLT tower in Melbourne in 2014. In 2008, dRMM, collaborating with Norwegian practice Helen & Hard Architects proposed 14-storey timber towers in Stavanger, Norway. These were designed as all-timber structures but eventually built in 2014 as a concrete and timber hybrid.

How high is high, when it comes to timber? Although unbuilt proposals compete for the title, including PLP’s 80-storey ‘toothpick’ designed for a site in London in 2016 via Cambridge University, in 2017 the world’s ‘tallest timber tower’ built is Brock Commons Tallwood House by Acton Ostry Architects for University of British Columbia. This uses the CREE concrete and timber with steel connector system devised by Hermann Kaufman and Arup. At 17 storeys, the first floor and cores are concrete and the wood above not visible as it is covered in drywall. The design intentions are laudably grounded in global environmentalism, but the outcome is ironically the language of steel frame construction, like 1960s Mies van de Rohe buildings now constructed in wood.

The sky’s the limit for the fast evolving world of modern timber construction techniques, and the architectonic expression of ‘new’ materials and forms remains underexplored. The relevant question is not how high can you go, but do you really need towers to achieve urban density? And if so, at what height does it stop making sense to use 100 per cent timber? The absurdity of structural perversity is the actual limit for timber construction. It is worth noting that the tallest trees (Californian Redwoods) are beautifully resolved structures, and rarely grow higher than 100 metres, circa 33 storeys.

For 20 years I have been advocating laminated timber’s outstanding versatility, weight to strength performance, sustainability, speed and limitless expression. Together with Arup and the American Hardwood Export Council, dRMM have invented and tested cross laminated hardwood; the 2013 Endless Stair installation was specifically created to demonstrate engineered timber’s massive potential for the 21st century construction industry. In 2017 we completed the first building using hardwood CLT, Maggie’s Oldham (which will be featured in depth in November’s ADF). This project showcases structural exposed tulipwood CLT, timber insulation, and a specially designed thermally modified external cladding, also tulipwood. The reason for inventing sustainable hardwood CLT was that it is lighter, stronger and more beautiful.

As a timber architecture specialist I hesitate to advocate very tall all-timber structures for the sake of simply being higher, or to pretend that what are inevitably hybrid structures are actually ‘timber’ towers.  Concrete, steel, glue and glass are always essential parts of the design; what is important is the ratios. To build 30-plus storeys high in 100 per cent timber, and whether as a frame or mass wood construction, currently means using more timber than is efficient; the top-down progressive loads mean that the lower levels of the tower would literally be a forest of wood.

The considered answer to this century’s architecture is not the ‘tallest timber tower’ but clever composite structures as well as new high density 6-12 storey building typologies; i.e. how you make sustainable cities. Mixing in but reducing steel and concrete to the absolute minimum, whilst exploiting timber’s unique ability to invert the construction industry paradigm for carbon production, pollution and waste, is the desired future.