Mass timber: mass appeal or a massive risk?

Introduction

The government recently unveiled its Timber in Construction roadmap to increase the use of timber in the construction of homes and buildings. The roadmap assesses both the opportunities and constraints for increasing the safe use of timber in construction in England; as using timber is seen by the Department for Environment, Food and Rural Affairs (DEFRA) as one of the key ways that emissions from buildings could be reduced.

One way to employ timber in construction is by the use of mass (or massive) timber systems. This blog considers this emerging trend and looks at why a mass timber system might be chosen over more traditional building materials, as well as exploring some of the commercial and legal considerations and concerns developers looking to get involved in mass timber projects may need to tackle.

What is mass timber?

Mass timber is an umbrella term used to refer to products which typically comprise layers of wood joined together to make strong panels which can be used to construct buildings. The term encompasses a number of products such as cross-laminated timber and glued laminated timber (otherwise known as "gluam").

There are already multiple mass timber commercial buildings in existence, including the Ascent building in Milwaukee (currently the tallest mass timber building in the world) and the Black & White Building in Shoreditch which officially opened in January 2023.  There are plans to construct further mass timber buildings in the UK in the future, even including a timber football stadium which will be the Forest Green Rovers' new playing ground.

Why use it?

Mass timber is considered to be an environmentally friendly alternative to more traditional building materials such as concrete, bricks and steel.  Not only is the process of constructing a building out of mass timber believed to be less carbon intensive than using these traditional building materials, but the mass timber components are also able to store captured carbon thus keeping it out of the atmosphere and potentially resulting in a net positive carbon impact on the environment.

Mass timber is not just an attractive material because of its sustainability promises, but also because of the potential on-site efficiency it offers.  A mass timber building can have a faster on-site build time than its traditional counterpart.  This is in part due to the timber components being pre-fabricated off-site meaning it can effectively be a matter of assembling these components together once they arrive on-site.  One "wood hybrid" building in British Columbia reportedly took less than 70 days to assemble on-site, which is apparently four months faster than a typical project of its size.

Restrictions

Despite mass timber's attractiveness as a sustainable and efficient building material, there are restrictions on the use of timber in construction.  For example, timber is categorised as a combustible material meaning there are certain regulations developers must follow when incorporating it into residential buildings.  A government review in 2022 clarified, among other things, that structural timber can be used in the external walls of residential building that are lower than 18m in height provided the materials are used in accordance with the Building Regulations requirements[1].  This is just one example of the restrictions applicable to the use of combustible materials in construction and a full discussion of this is beyond the scope of this blog post.  For more information on this, the Government review on the ban of combustible materials provides a helpful introduction.

Considerations and concerns

Insurance

Unsurprisingly, insurers have raised some concerns over the perceived risk of fire in relation to use of timber products in construction. There are also concerns regarding mass timber's susceptibility to water damage. Timber can also be impacted by humidity and UV exposure, and insurers may have concerns over the time required to restore business function following an insurable event.

However, these concerns do not amount to a wholesale rejection of mass timber projects by insurers. The DEFRA Timber in Construction Roadmap notes that efforts to increase collaboration with insurers, lenders and warranty providers are already underway, such as the Mass Timber Insurance Playbook, which provides risk mitigation guidance. The government is also looking into the feasibility of creating a risk register of anonymised data on mass timber buildings, including international data, and is looking to facilitate greater dialogue between the insurance sector and developers.

Potential practical solutions to concerns surrounding fire and water damage also already appear to be emerging.  "Hybrid" structures, which feature mass timber components but also include a concrete or steel core, are an example that could assist to allay insurers' concerns.

Supply chain

In order to build a mass timber building, developers need to be able to source the timber product itself and this can be impacted by supply chain issues.  For example, it has been noted that rising popularity of timber in the US market could affect the availability of timber in the UK market and increase its prices by effectively "sucking" the timber out of Europe (where the UK sources a proportion of its timber from). One of the priority themes in the DEFRA Timber in Construction roadmap is to increase the supply of sustainable timber.

Developers will usually also want to ensure that they are sourcing their timber responsibly.  Organisations such as the Programme for Endorsement of Forest Certifications (PEFC) attach their certification to timber originating from forests which are managed sustainably and in line with international requirements[2].  The PEFC has designated all timber originating from Russia and Belarus as "conflict timber" indefinitely, meaning it cannot be used in PEFC-certified products.

Off-site materials

As mentioned, one of the possible benefits of using mass timber in construction is that it can result in faster on-site build times as much of the work on the timber components happens off-site.  However, this also introduces a level of risk, as the employer will be paying for materials which are not yet on-site and raises concerns surrounding the materials not being delivered due to the insolvency of a contractor, for example.  Therefore, mass timber developers will need to consider relevant legal protective measures such as vesting certificates and off-site materials bonds.

Conclusions

In an increasingly environmentally conscious market, mass timber offers an attractive sustainable alternative to more traditional building materials.  However, its use is not without limitation whether in the form of legal restrictions, insurers' hesitancy or supply chain issues.  The points set out in this blog post cover a handful of the factors that would require thorough consideration by developers before embarking on a mass timber undertaking, but also showcase the exciting potential of this emerging trend.

[1] https://www.gov.uk/guidance/ban-on-combustible-materials

[2] www.pefc.org