Andy Heyne, Founding Director at Heyne Tillett Steel, picks out some of the key arguments that divide current opinion most, and offers some thoughts about how to converge and create consensus on its use.
This year I celebrated my thirtieth year as a structural design engineer in London, more recently focusing in the commercial office sector for private developers in London. Structurally projects tend to either be majority retrofit with large lateral or vertical extensions, or wholesale new buildings, the balance perhaps shifting towards the former with the drive to lower carbon and ‘retrofit-first’ policies increasingly being introduced by local planning authorities. Appetite and opportunity to use mass timber has always waxed and waned since the dawn of commercial availability, but ironically now, as we have increased lived experience and many examples of award-winning completed buildings, the tidal swing of split opinions is greatest. Has timber become marmite?
“Timber costs more, and in difficult economic times where margins are squeezed, any extra cannot be justified.” This ‘premium/delta’ is perhaps less than people think and needs market testing with early supply-chain input to ensure accuracy. Also, other benefits of timber are not always considered holistically alongside, such as reduced programme, substructure or strengthening (when adding floors) savings, or even increased value/let-ability. Our homework is to make sure we accurately quantify the cost of these wider benefits and build them into any appraisal for timber frame.
“Insurance is harder to obtain and significantly more expensive.” We must be honest – timber buildings do have a higher risk profile, less so a fire issue now with specialist fire engineers, established detailing and largescale testing. However, sadly it is clear many roofs leak regardless of structure, yet timber is more susceptible to water and so claims resulting from water damage requiring timber repair are on the rise. In my experience, leaks occur more in-service (poorly installed and maintained pipework, and roof finish failures) than during construction. Where water management strategies are now established, they have better continuity when passed from timber specialist to main contractor. In response, during design we now have a range of both passive and active risk mitigation measures we discuss on each project with the team (moisture sensors, shallow slopes, weepholes etc), balancing risk against capex and design impact. We are yet to see how these perform specifically, as most now-leaky timber roofs were conceived prior to this level of consideration, and our current strategy is now to offer timber roofs as a solution alongside others, but not to pro-actively encourage them, at least until we have regained confidence that the mitigation is working.
“Lower carbon costs more/gives me no commercial benefit.” There is currently not enough regulation to force, or financial incentive to encourage, developers to pursue mass timber. In such difficult economic times this is probably correct, even if the drive to net zero will regrettably slow in the short-term, as any regulatory tightening would result in less projects progressing to site. However, with hoped improved conditions in the not-toodistant future, lower carbon will undoubtably provide a calculable commercial advantage, whether through planning concessions, increased rent/let-ability with more progressive tenants, or perhaps a lower cost of carbon offsetting to finally and legitimately label buildings ‘net-zero’. You heard it here – commoditisation of stored carbon, the new global currency!
“Mass timber is not cool anymore – it’s a tired and overdone aesthetic. Where before it was trendy and ‘insurgent’, is it now commonplace and ‘incumbent’.” Are we all less excited about it now? When faced with any negativity or challenge, combined with a weakened carbon incentive, are we perhaps less likely to have sufficient critical mass of conviction to drive it through as a solution? I understand the sentiment here, perhaps as mass timber was once touted as a panacea or ‘silver bullet’ that feels like it never quite fulfilled its potential, but I honestly believe its popularity will re-emerge when better economic conditions are restored.
So how can we remain positive about the prospects of widescale mass timber usage in commercial buildings across the UK? For people like me, who for the past 20 years have been on the stop-start mass timber ‘train’, this feels like just another obstacle on the tracks. The onestep- back after two-steps-forwards.
We’ve been here before, and I suspect we’ll be here again – the obstacle will be removed, because we have learned to remain agile and creative, to adapt and find solutions, technical and political. And frankly we have no choice, because the impending climate catastrophe is not going away, and large-scale mass timber buildings are one of the most potent counter-weapons in our arsenal… oh and I really don’t like marmite!
