Insuring mass timber

This article originally appeared in the April 2024 issue of the Fire Protection Associations' Fire & Risk Management Journal.

Mass timber has become an increasingly popular choice of material within the construction industry. Whilst a renewable alternative to traditional building materials, the challenges faced in the use of and the insurability of buildings adopting mass timber products has recently been the subject of discussion.

What is ‘mass timber’?

Developers and builders alike have recently been made alive to the inherent strength, adaptability and environmental benefits of these wood products to create a wide range of sustainable and ambitious structures. Products falling under the ‘mass timber’ umbrella include cross-laminated timber (CLT), glue-laminated timber (glulam), and laminated veneer lumber (LVL).

Using various combinations and sizes, mass timber products can serve as beams, columns, floors, roofs and walls considering the directional strength of each wood product. The use of mass timber products can often result in faster construction times, reduced waste, and lower carbon footprints.

The environmental advantages of mass timber are significant - wood is a renewable resource, and the use of mass timber promotes sustainable forestry practices.

Fire performance of mass timber

Mass timber products have the potential to exhibit impressive fire performance characteristics under certain conditions. When exposed to fire, wood forms a layer of char that insulates the unburned wood beneath, effectively slowing down the spread of flames and maintaining structural integrity. This process, known as charring, provides mass timber with inherent fire resistance, allowing it to withstand fire exposure for extended periods.

Mass timber structures may therefore perform well in real-world fire scenarios due to their robust construction and predictable behaviour. Unlike steel, which can rapidly lose strength and collapse when exposed to high temperatures, the charring of wood is a gradual process. This may in turn increase fire resistance, therefore slowing the spread of a fire within a building and allow more time to respond.

Fire and water and mass timber?  

Despite its obvious benefits, the inherently combustible nature of wood raises concerns regarding the fire safety of mass timber structures. The potential for rapid fire spread and structural failure in the event of a fire raises significant risks to occupants and firefighters alike.

The inherent nature of wood also raises questions as to the ability of mass timber products to survive water exposure and/or escape. Both scenarios raise concerns generally about the suitability of mass timber for a proposed project/structure.

These concerns also raise important questions on which insurers require clarity to reach an informed decision on policy cover and its scope. Insurers require clarity as to a building’s risk profile to make an accurate assessment of the potential for claims and types of loss. For example, design features that may allow the spread of fire within or over a building and impact structural integrity may determine insurers' assessment.

The Mass Timber Insurance Playbook

How can these issues be addressed? The Alliance for Sustainable Building Projects published the Mass Timber Insurance Playbook (‘the Playbook’) in May 2023. One of its key objectives is to enable a collaborative approach between construction teams and insurers. Its aim is to help stakeholders in the insurance and construction industries understand each other’s priorities, and thereby enable engagement to overcome any gaps in risk management and coverage which may hold back mass timber construction.

Key components of the Playbook include:

  • Risk assessment: Conducting thorough risk assessments to identify and mitigate potential hazards associated with mass timber construction, including fire risks, structural integrity, and environmental factors. Typical measures to mitigate fire risk may include fire suppression systems, features to encourage the effectiveness of access for fire services, and design features to prevent or minimise the route of fire spread. As to the latter, one particular challenge faced (aside from the use of delaying devices such as cavity barriers) is the prevention of fire spread in combustible voids. This risk can be mitigated via the design and use of fire resistant materials to either line, sprinkler-protect or fill such voids. Whilst doing so will likely allow firefighters more time to deal with the fire, it will undoubtedly also delay fire spread (particularly given challenges faced with the seemingly unnoticed spread of fire via combustible voids) and the extent of any damage. This, combined with the fire performance potential of the mass timber product itself, may well demonstrate exceptional overall fire resistance characteristics compared to traditional construction materials.
  • Building design and construction: Implementing fire-resistant building designs and construction techniques to enhance the safety and resilience of mass timber structures. This may include the use of fire-rated materials, sprinkler systems, and compartmentalisation strategies.
  • Insurance coverage: Working closely with insurers to secure appropriate coverage for mass timber projects, including property and liability cover, as well as any additional endorsements for specific fire protection measures.
  • Risk management strategies: Implementing risk management strategies to minimise the likelihood of fire-related losses and effectively respond to emergencies. This may include developing evacuation plans, conducting regular fire drills, and investing in fire detection and suppression systems.
  • Industry collaboration: Facilitating collaboration between insurers, developers, architects, contractors, and fire safety professionals to share knowledge, best practices, and lessons learned in mass timber construction.

Implications for Insurers

The increasing adoption of mass timber in construction projects has significant implications for insurance coverage. Insurers assess the risk associated with a building based on various factors, including construction materials, location, and occupancy type. Absent the Playbook and the collaboration it seeks to establish, insurers may typically perceive mass timber products to be too high a fire risk compared to traditional construction materials like concrete and steel. This may result in increased premiums where cover is in fact provided.

Reliance on the Playbook should ultimately allow insurers to better understand the risk being taken on. It does so by clarifying the adaptability and ‘cutting edge’ nature of the material being used, its increased performance against traditional materials whilst ultimately, contributing to ‘net zero’ aims for all those involved. 

The Playbook also sets out the following ‘high-level’ factors to allow insurers to make an informed decision on whether to cover mass timber projects:

  • Occupancy: the functional purpose to which the building is put
  • Scale: the scale of the building and any sub-compartment in association with its proximity to other buildings
  • Structure and fabric: including building structure material, ground floor structure, construction method and core/overall structure
  • Other risk factors: such as internal car parks, balconies, swimming pools, hazardous materials, green surfaces and green energy systems
  • Fire and water mitigation: the role such mitigation measures may play in reducing likelihood of loss and/or scale of loss

Insurers will have to consider the importance of these factors together with the mitigation measures put in place to reduce or minimise all challenges.


Mass timber represents a sustainable and innovative solution for modern construction, offering numerous environmental, structural, and design benefits. In light of key policy ambitions around environmental sustainability and a ‘net zero’ future, mass timber products offer a unique and exciting opportunity for all those involved within the construction sector. Whilst the adoption and use of mass timber is visible in various parts of the world, the scale of the mass timber market within the United Kingdom is undoubtedly hampered by a lack of investment in production facilities.

Given the benefits of the adoption and use of mass timber products, any increase in such use will be led by an increase in demand for manufacturing to take place within the UK. This will need to be coupled with a greater knowledge and understanding within the industry regarding the manufacturing, design, and construction possibilities of all forms of mass timber.

The Playbook is therefore a ‘step in the right direction’ in increasing the adoption and use of mass timber products within the UK. It is however vital for those involved within the industry to continue collaborative efforts in understanding the risks involved and how to mitigate against those risks.

Chief amongst those concerns is that of fire safety, especially given the recent tragic examples of Grenfell and in Valencia, Spain. This is particularly so with the challenges faced by insurers in understanding the level and extent of risk to be insured. In turn, this may positively impact the level of ‘comfort’ in adopting the use of such products.

Removing or minimising the associated risks and applying pertinent mitigation measures will show that the adoption of mass timber products is truly underway. This increased adoption should, in turn, reduce any environmental impact via decarbonisation and thus bring us a step closer to ‘net zero’.

Read other items in Construction Brief - June 2024

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