Until recently, there was a growing movement in the UK to build tall buildings using timber.
There are ancient Chinese timber pagodas which are many storeys high, but going tall with timber is something the western world has struggled to embrace, despite the abundant timber natural resources, and structural benefits of timber.
There are two key reasons, firstly the 20th century dominance of concrete and steel, and secondly, fire.
And Grenfell Tower obviously only further increased the focus on fire risk when it comes to constructing tall buildings.
Surely we need a national, exhaustively rigorous testing programme to clear this up.
A blunt response
The Government reacted in what some might say was a blunt fashion following the Hackitt report, banning all ‘combustible’ materials in the external walls of newly constructed towers over 18 metres.
While Grenfell was undoubtedly a tragedy, whether or not simply banning materials which can burn – rather than immediately putting the focus on issues around Building Regulations – is the best way forward, is up for debate.
As many timber aficionados will tell you, timber is a suitable material for constructing multi-storey buildings, and several recent projects have shown it’s being tested to greater limits structurally than ever before.
In Norway – Voll Arkitekter’s 85.4 metre, 18-storey tower in Brumunddal has just been named the world’s tallest timber building.
Mjøstårnet is a mixed use resi, hotel and office scheme, and shows what can be done, albeit in a country full of forests and already well used to large-scale timber building.
It’s made of big glulam trusses, with a CLT (cross laminated timber) core, including lifts and stairs.
The project took the title from a student accommodation building in Vancouver called Brock Commons Tallwood House; this was a ground-breaking timber structure at 53 metres, but had a concrete core.
The UK has also been pushing the envelope, with Waugh Thistleton architects’ Dalston Works claiming the title of the world’s largest CLT building (in terms of floor area) in 2017. Stadhaus in Hackney – a hotbed of CLT adoption – was the first tall all-CLT apartment block, in 2009.
Is this the end for timber?
Despite all this innovation, particularly in CLT, the Government’s actions seem to have heralded the end for timber in tall UK buildings.
The ban permits only materials with a Class A1 or A2 rating in the external wall – with a failure to explicitly exclude CLT, the move has been perceived to forbid its use in external walls.
This doesn’t mean to say that with the great modular, sustainability and wellness benefits timber offers, it can’t be used in sub-18 metres buildings all over the country, which includes a lot of potential resi, but the likelihood of it ascending to skyscraper level is certainly curtailed.
Is CLT a panacea?
CLT is great for modular housing application, which is why its been eagerly taken up by a range of organisations keen to innovate to deliver the housing numbers needed, evidenced in Legal and General and Swan Housing Group’s investment in modular housebuilding factories.
There are differing views on the sensitive issue of fire performance which has been thrown into starker relief since Grenfell, although no timber was used in its structure.
Some (including obviously on the ‘timber lobby’ side) believe the charring properties of the materials can actually make it safer than steel in certain cases.
Others believe that research exists to prove that CLT is not the panacea, even if only used on internal walls and floors.
Some form of national, exhaustively rigorous testing programme is surely now needed to clear this up.
Changing cities into forests
In the meantime, other countries are confidently heading skyward with timber buildings.
Japanese timber supplier Sumitomo Forestry is planning to showcase its product in an unprecedented way, with a proposal for a 350-metre skyscraper in Toyko, one metre for every year the company will have been in operation, by its completion in 2041.
While it would be a hybrid of steel and timber structurally, this would be a striking and perhaps even brave attempt to show what timber can do to “change cities into forests.”