Architettura in legno
Why do architects want to build high? Especially in timber?
Like testosterone-fuelled explorers driven to go further, the challenge is simultaneously unessessary and irresistible. The biggest erection wins the global reputation, the research stakes, the media interest, the TED talk and most of all the short-lived title, the World’s Tallest Timber Tower…
How high is high in timber? Although way higher unbuilt proposals compete for the title of world’s tallest timber building, currently the tallest CLT timber tower completed is still ten storeys; the 2012 Forte by Lend Lease developers in Melbourne, who were introduced to cross laminated timber (CLT) by the author in 2009. This has been surpassed by a timber framed tower of fourteen storeys in Bergen, Norway, by Artec.
dRMM Architects have pioneered engineered timber architecture in the EU, exhibiting the first CLT flatpack prototype house in Oslo in 2006, and UK school buildings from 2007. In 2009 dRMM proposed an engineered timber 6000 seat Handball Arena for the 2012 London Olympics, and ten storey CLT apartment building designs to developer Lend Lease for the Athelete’s Village. Too ahead of its time, these were built in concrete, as was the rest of the London Olympic project. 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 hybrids.
In 2016 the news is full of competing designs and projects due to go ahead for much taller timber towers. The main contenders in the race for height are Architekten Herman Kaufmann of Austria, who has designed a 30 storey timber/concrete hybrid structural system with ARUP entitled Lifecycle Tower, and MGA of Canada with a tower of 35 storeys proposed with DWD for Reinventer, Paris. The design intentions are laudably grounded in global environmentalism, but the outcome is the signature architecture of towers. Ironically, the typologies proposed speak the language of steel frame orthodoxy, like 1960’s Mies van de Rohe’s high rise buildings made in wood.
In an age which has forgotten that everything used to be built in timber, the strategy of employing familiar forms but with a substitution of construction material is a reassuring way to put clients at ease. The perception of the ‘risk’of using ‘new’ construction materials is assuaged by the orthodoxy of the architecture of the right angle.
But the sky’s the limit for the fast evolving world of modern timber construction techniques, and the architectonic expression of ‘new’ material and form 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, which rarely grow higher than 100m, circa 33 storeys.
For 20 years I have been, through dRMM and academe, the first to advocate laminated timber’s outstanding versatility, weight to strength performance, sustainability, speed and endless attraction. Together with ARUP and the American Hardwood Export Council, dRMM invented cross laminated hardwood; the 2013 Endless Stair was specifically created to demonstrate engineered timber’s massive potential for the 21C construction industry. But as a timber architecture purist I hesitate to advocate very tall all-timber structures for the sake of simply being possible or higher, or to pretend that what are actually hybrid structures are ‘timber’. Concrete, steel, glue and glass are always essential parts of the design; what is important is the ratios. To build 30+ storeys high in 100% timber, whether as a frame or mass wood construction currently means using more material 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 is not the tallest timber tower, but clever composite structures as well as new high density building typologies. Mixing in but reducing steel, concrete, and carbon to the minimum, whilst exploiting timber’s unique ability to invert the construction industry paradigm for carbon production, pollution and waste, is the future.
But cities are not made by housing alone, and the appetite for land that high rise development demands is creating other issues. A result of the housing crisis in London is a growing exodus of manufacturing and service-based industries. The demand for housing combined with exorbitant investment profitability, coupled with change of use Planning policies means competition amongst residential developers to aquire urban land is acute. Consequently, large or medium sized inner city sites are far too costly to justify the classic industrial single storey shed typology. The traditional compound of ground level light industrial workshop units arranged around level access is no longer economically viable.
dRMM’s modest response is the Stacked Workshop engineered timber prototype. This development operates on the premise of exploiting inner city sites for workspace that are too small, too difficult, and not desirable enough a location to offer serious residential development; therefore the land is affordable.
A small footprint, lift-access Light Industrial workspace typology has been designed, offering a medium-rise modular CLT timber structure as high density ‘start-up’ workshops. The first 14 unit example goes on site in Greenwich in 2016.
The land usually needed for the generic single-storey compound of light industrial steel sheds, arranged around vehicule access, would have been circa Xm, depending on layout and parking provision.
Steel manufacturing produces more carbon than steel. The average CO2 intensity for the steel industry is 1,9 tons of CO2 per ton of steel produced.* A tonne of structural timber represents minus 1.6tons of carbon, thanks to sequestration. The automatic light industrial steel framed building, clad in steel or alu siding, is inherently high energy, environmentally and architecturally dumb. The engineered timber and glass Stacked Workshop design proposed provides the same amount of, but arguably better workshop accommodation, but uses only Ym of land, and is carbon hoarding. Deliberately not sky high, but high density and low energy. A modest new typology to make cities work for people and planet.
*M. Kundak et al.: CO2 Emissions in the steel industry
Professor Alex de Rijke
Director dRMM Architects