It has been predicted that, due to an ageing workforce, 620,000 people will have retired from the construction industry by 2026.¹ Replacing these workers will require greater efforts by government and industry to coordinate, consolidate and communicate the opportunities and advantages of working in construction to students, ensuring there is sufficient funding for apprenticeship provision, and at least partially offsetting these shortages through investment into MMC.

Many of these issues were captured in Mark Farmer’s landmark 2016 review of the UK construction sector. The report called for purposeful and strategic industry leadership to drive investment in new technology and manufacturing capability which will grow over time to boost capacity, productivity and reduce the reliance on labour in line with the likely future reducing availability. The residential sector was suggested to lend itself most easily to a large scale move to a manufacturing led approach, with the ability for MMC to evolve into other sectors subsequently.

Where does timber sit within MMC?

Timber should have a natural advantage in this new policy environment. An emphasis on speed creates a preference for offsite, and emphasis on offsite creates a preference for timber. This is because timber is a light, versatile material which lends itself to manufacturing processes.

Timber has a long history as a forerunner of MMC, and offsite construction, through timber frame. Structural timber technology is proven, and already accounts for 83% off homes in Scotland, where a healthy, profitable house building industry has thrived for decades. In England, timber frame now accounts for 23% of newbuild homes, following year on year growth since the 1980s where timber frame accounted for around two percent of housing starts.²

Engineered timbers are continuing to expand the range and use of MMC and timber in construction. These forms of timber are designed to meet very specific performance requirements or needs, while retaining many of the advantages of solid wood. While they are designed and manufactured offsite, they can still be easily reworked with ordinary tools and basic skills, and as with any wood product, engineered timber sequesters. Some engineered timber products, such as CLT and glulam, are pound for pound stronger than steel.³ Increasingly engineered timber is being chosen to displace steel and concrete in mid-rise buildings, including high profile projects such as the headquarter for Google.⁴  which can lead to an average embodied carbon saving of around 60% according to research from Bangor University.

Engineered timber can also be made from small pieces of wood, wood that has defects, or species which are not otherwise able to offer a commercial use. This adds additional efficiency into the timber supply chain. Offsite construction using engineered products means buildings can be completed quicker, quieter, and cleaner with minimum disturbance to communities.

How is MMC being adopted in the UK?

Entrenched practices, low levels of investment into research and development, lobbying by competitors and low productivity have created an industry which is slow to embrace innovation. However, progress is being made – and accelerated – in part thanks to industry unity to ‘build back better’ following the COVID-19 crise, a preference for modular construction for new build projects, and the appointment of Mark Farmer as the government’s Champion for MMC.⁵

According to Mark Farmer, the volume builder world still views MMC and offsite as unknowns. There is a perception of financial risk, with MMC considered ‘unproven’, and the upfront costs off-putting.⁶ However, this is changing, as can be seen through the creation of ‘in-house’ timber frame offsite manufacturing by housing associations such as Accord, the largest not-for-profit housing organization in the Midlands, or the ‘Wood First’ preference and use of CLT by Hackney City Council.⁷

Across the UK there are thousands of high-quality homes built using timber frame every year, and the Structural Timber Association (STA) says the capacity already exists to double output.⁸

What are the sustainability credentials of MMC?

The use of CLT by Hackney City Council in buildings such as Dalston Lane highlight the enormous potential of MMC, which achieved 3,576 tons of sequestered carbon and 976 tons of embodied CO2. This delivered a net carbon footprint of -2,600 tons CO2.⁹ An equivalent building made with a concrete frame would result in an estimated +2,000 ton of CO2 being emitted. In effect, the carbon which was embodied in Dalston Lane is equivalent to the emissions produced by 1,703 cars over a year.¹⁰ CLT is not alone in delivering environmental benefits, which are natural to using sustainable timber.

Timber frame construction on average reduces carbon emissions by 20% when used in place of carbon intensive materials such as masonry, steel or concrete.¹¹ Timber frame is the largest method of offsite construction in the UK, and can deliver many benefits, in quality, speed of construction, and technological performance, while delivering reliable profit margins and for investors.

Other environmental benefits of MMC, besides this considerable reduction in carbon emissions, include fewer deliveries, fewer defects, and up to 90% less waste.¹² Collectively this reduces the number of vehicles travelling to and from construction sites, both to drop off products, and picks up waste. Sustainable timber supply chains are recognised as an important form of greenhouse gas removal, and the UK Committee on Climate Change has consistently recommended the UK increase the use of wood in construction.¹³