5 minute read
Good with wood?
The government needs to build 300,000 new homes in England per year while achieving zero carbon emissions by 2050. Construction 2025, a joint government and industry strategy, has outlined targets for the UK construction sector, including halving constructionrelated emissions and project delivery times, and reducing construction costs by a third, by 2025. These ambitious goals are made no less so by the industry’s reliance on concrete, “the most destructive material on Earth,” according to The Guardian.
According to the All-Party Parliamentary Group (APPG) for the Timber Industries’ report, How the timber industries can help solve the housing crisis, if 270,000 of these new homes were to be built by the timber industry, three million tonnes of carbon dioxide would be absorbed and stored each year and build times would be 30% quicker. The report goes on to argue that using timber in construction is central to meeting emissions targets and urges the government to implement the recommendations of the Climate Change Committ ee by increasing the use of timber in construction.
Sustainability credentials aside, the human cost of the housing crisis cannot be ignored. As the report notes: “The housing crisis in the UK has a fundamental and negative eff ect on our quality of life. A lack of aff ordable housing is consistently linked to poverty, poor mental and physical health.” Success in creating a fl ourishing housing industry, and in turn, a fl ourishing timber industry, would be felt right across the country.
Off site timber-frame construction
Throughout the 1950s and 1960s the UK building industry moved towards industrialised forms of building, and in the early 80s prefabricated housing became dominated by timber-frame systems. Timber-framed dwellings grew steadily to around 30% of the new-build market until negative media coverage and the public’s continued general suspicion of modern construction methods contributed to a signifi cant downturn in production. Until recently, this stigma has remained. Perceptions are very diff erent in Scotland where timber frame remains wellrespected, with production hardly aff ected and timber frame continuing to account for 75% of all new houses.
Quite rightly, we’re now seeing a shift in mentality throughout the rest of the UK. It’s a method that combines speed, quality and effi ciency; all of which contribute to aff ordable, low-carbon, effi cient homes. Today’s off site timber-frame homes – thanks largely to technological advances – are also high quality. Off site construction’s controlled approach to planning and constructing buildings signifi cantly minimises any room for error, and gives opportunity for new eco-friendly process planning, designing and installing within a much-reduced time frame and budget. The factory sett ing allows bett er quality control of “CLT is easy to transport and modify, reduces noise pollution on site and is highly cost effi cient”
Jeremy English, Director at Södra Wood, believes timber is the answer to the building industry’s problems, if only it can give up concrete…
materials, chain production setups and easier implementation of processes and manufacturing methods. Research published by WRAP also demonstrates that the use of timber-frame construction components can reduce the amount of waste generated on site by up to 40%.
According to the NHBC, timber-frame construction currently accounts for just 15% of UK housing output. The benefi ts outlined above, coupled with the fact that government housing targets simply cannot be met through traditional methods alone, makes me confi dent that this fi gure will increase exponentially in the years to come.
The elephant in the room
No current conversation about timber is complete without comment on the government’s catch-all ban on combustible materials. At the end of 2018, as part of fi re safety improvement measures intended to prevent another tragic blaze like that seen at Grenfell Tower, the then Housing Secretary, James Brokenshire, introduced new legislation banning combustible materials on new high-rise homes above 18m. The government is now considering lowering the height threshold for combustible materials to at least 11m according to current Housing Secretary, Robert Jenrick.
Architects, builders and suppliers of timber and engineered timber products are looking at what the future holds for mass timber builds following this catch-all ban and, in particular, the specifi cation and use of cross-laminated timber (CLT) as a strong, lightweight structural component for multi-fl oor structures.
While there’s no question that these restrictions are intended to enhance occupant safety, we mustn’t lose sight of CLT’s inherent benefi ts; benefi ts that have made it an increasingly popular choice for structural components since its introduction into the UK in 2004. It’s easy to transport and modify, it reduces noise pollution on site and it’s highly cost effi cient to produce and use.
Available testing evidence indicates that structural timber and CLT products also have predictable charring rates. When exposed to fi re, the load-bearing core of a beam or truss will remain intact while the char layer remains to protect it. The char forms an insulation
layer preventing an excessive rise in temperature within the unburnt core. The core continues to function, providing a predictable period of fi re resistance.
As Andrew Waugh of Waugh Thisleton Architects, one of the UK’s leading proponents of timber construction, notes: “The reality is that the evidence says we’ve got 12 years left to sort out climate change – we’ve got to start changing the way we do things. And we’ve got to keep pushing the message about the safety of CLT. It’s not only quicker to put up; it’s safer, healthier, lighter and locks away carbon.”
Presently, the Structural Timber Association, among others, is currently augmenting its already extensive fi re-resistance testing data. Further investigation will determine how the in-situ fi re resistance characteristics of structural timber systems can be best exploited in modern high-performance buildings. Once they arrive, I believe we should then have an informed review of regulations.
