When is Timber Timber?

When it's concrete (steel, brick, glass, aluminium)

Everyone's building timber towers. Well not everyone. dRMM's Alex de Rijke, on why he doesn't believe the tall towers rush is where it's at.

Why do architects want to build high? Especially 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 naturally the short-lived title, the World’s Tallest Timber Tower…

dRMM Architects were pioneers of engineered timber architecture in Europe, exhibiting the first cross laminated flat pack prototype house in Oslo in 2006, and realising state school buildings from 2007. In 2009 dRMM proposed a 6000 seat Handball Arena for the 2012 London Olympics, and a ten storey all-timber apartment building design to developer Lendlease for the Athlete’s Village – see this Unstructured Extra’s dRMM and CLT feature. This, too ahead of its time, was built in concrete frame, but Lendlease went on to build the ten 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.

dRMM's Nordic collaboration with Helen & Hard on their Rundeskogen
timber concrete hybrid towers – Photo Emily Ashby (also above)

A decade later many architects want to build in timber, and predictably they want to build high. But how high is high in timber? Although unbuilt proposals compete for the title, including the 2016 PLP Architects 80 storey ‘Toothpick’ in London via Cambridge University, last year 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 ARUPS. At 17 storeys, the first floor and cores are concrete and the wood above not visible as covered in drywall. The design intentions are laudably grounded in global environmentalism, but the outcome is ironically the language of steel frame construction, like 1960’s Mies van de Rohe buildings now made of 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 which height does it stop making sense to use 100% 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.

LCT 1 by Hermann Kaufmann, Mies IBM Plaza, Chicago, and ActonOstry's University of British Columbia's 17 storey student dorm timber tower – Photo's Hermann Kaufmann Arkitekter, Open Source, Wikipedia, and ActonOstry

For 20 years I have been, and continue to be, the first UK architect to advocate 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. 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.

Taller than the trees - Californian Redwoods – Photo Michael Nichols
Flat pack - dRMM’s Maggie’s Centre in Oldham – Photo Alex de Rijke (and below)

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 are the ratios. To build 30+ storeys high in 100% timber, whether as a frame or mass wood construction means using more timber than is efficient; the top-down progressive compression 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.

Alex de Rijke is co-founder of dRMM and has been at the forefront of engineered timber advocacy in Britain and internationally.

This piece originally appeared in the Australian Architectural Review magazine