Mass timber is a construction method that offers sustainability benefits such as reduced greenhouse gas emissions, construction efficiencies, aesthetic appeal, and strong marketability. Due to these factors, mass timber has seen rapid growth, with thousands of projects underway at present. By understanding and addressing the inherent risks around fire and water, stakeholders can maximize the success of mass timber construction projects.
What Is Mass Timber?
A mass timber project is defined as a construction project that incorporates structural elements of large dimension engineered wood products, such as cross-laminated timber (CLT), nail laminated timber (NLT), dowel laminated timber (DLT), and glue laminated timber (GLT)—with more types in development all the time. This includes hybrid systems that also utilize concrete and/or steel, along with mass timber structural elements.
The common thread is that these products utilize regular dimensional lumber to create large, multi-layered, engineered members that overcome many of the challenges associated with smaller lumber. It is strong, consistent, stable, and able to be used in structural systems in buildings exceeding, so far, 280 feet, far beyond the capabilities of light wood frame.
These materials all share risk factors, and, therefore, have similar planning and construction concerns. In this article, we will focus on the two primary risks that have led to insurance claims: fire and water.
What Is the Status of the Mass Timber Market?
In a word, the mass timber market is growing. As of June 2025, there are 1,217 projects in design and 1,307 projects under construction or built, for a total of 2,524 projects, reports Woodworks.org. Compare this with 500 in 2020 and 1,000 in 2023. Some industry predictions suggest there could be as many as 24,000 mass timber buildings by 2034, The New York Times, reports. According to Allied Market Research, the global mass timber construction market generated $857 million in 2021, and is anticipated to generate $1.5 billion by 2031.
As mass timber construction grows, it presents new challenges to builders and their insurers. Reducing that risk is essential to realizing the full benefits of building with mass timber.
Why Is Mass Timber Usage Increasing?
It is well known that the cement and steel industries are both heavy producers of greenhouse gas emissions and difficult to decarbonize—though many are working to improve, and making progress. Relative to those materials, building with mass timber can reduce the emissions associated with building materials by 13% up to as much as 26.5%, according to the U.S Department of Agriculture (USDA) and it is also a renewable resource.
Mass timber may also provide construction advantages, including a shorter installation timeline, reduced labor demand, and a lighter weight that requires less foundation support. It also requires fewer interior finishes, as it can be both structural and a final finish material. When utilized in this way, it offers visual appeal, as the exposed wood interiors create a warm, inviting, and modern aesthetic.
Mass timber may also lead to higher occupancy, as the effects of biophilia—the love of being in more natural-feeling spaces—leads to a demand for the construction type.
Causes of Loss
The risks and benefits of mass timber construction vary depending on several factors, including the project’s intended use, location, and structural components. There is no “one-size-fits-all” guidance for mass timber project risks, but there are certain consistent themes, and this paper is focused on two that have led to insurance claims: fire and water.
While fire may be the first thing that comes to mind when talking about wood construction, the fire-resistive qualities of mass timber and robust fire management practices have been effective. The main cause of loss has instead been water and rainfall related. Many of these instances could have been prevented or significantly minimized by the practices listed below.
This does not mean fire is not a concern, however, especially during construction, when mass timber buildings are most vulnerable and have an incomplete fire protection level, as fire protection measures like sprinkler systems are not yet fully installed and operational and there is a lack of fire compartmentation. This was tragically demonstrated recently through the Messager fire in Paris. The exact cause of this July 2025 fire is unknown, but it is currently being attributed to the lack of fire protection measures on the exposed, combustible mass timber materials during the construction phase. Key vulnerabilities included unprotected structural elements and façade panels; the potential presence of a high-combustible fire load from site equipment; and the need for more rigorous, system-level fire safety protocols during construction to mitigate risks associated with mass timber.
What Should Builders Do to Encourage Project Success?
Much of the below may seem very much like business as usual for a construction project, however taking the time to understand how to apply these techniques specifically to mass timber is well worth the investment of time and effort. Collaborate with all strategic partners to thoroughly think through and plan for fire and water risks specific to mass timber.
Preventing and mitigating fire:
- Assign fire safety to a responsible person who should create a fire risk assessment, a fire safety plan including equipment and training, and monitor compliance.
- Facilitate ongoing coordination and communication with local fire department.
- Establish emergency procedures, including escape routes and location of hydrants and equipment.
- Include mass-timber-specific messaging in site orientations for all on site.
- Have a hot works permitting program, including an extended fire watch period.
- Incorporate temperature/smoke monitoring technology.
- Utilize fencing and a guard service or technology for site monitoring and security. This helps prevent both arson and vandalism.
- Keep a clean site with enhanced housekeeping.
- Enhance diligence around all permanent and temporary electrical supply installations, minimizing the amount of temporary power where possible and ensuring it is installed properly, turned off when site is unattended, etc.
- Instate regular inspection of all corded tools and extension cords.
- Define a fire-resistant area for combustibles and battery storage.
- Ensure elevated diligence around use of temporary heat and reduce if possible or consider less hazardous methods.
- Place controls on smoking, with designated smoking areas away from building—if allowed on site at all.
- Ensure vehicle parking, fueling, and charging are in designated areas away from building and combustible materials except as necessary for loading/unloading.
- Maintain dry vegetation cleared a minimum of 65 feet from the building.
Preventing and mitigating moisture/ water risks:
- Assign water management to a responsible person who should create a moisture risk assessment, and a water removal and mitigation plan, including equipment, training, and compliance monitoring.
- As with fire prevention, include mass-timber-specific information in site orientations. All project personnel need to understand that this material requires a different mindset.
- Store mass timber properly prior to installation following best practices and manufacturer recommendations.
- Focus on enclosing the structure as quickly as possible following mass timber placement.
- Monitor and plan for weather or water events; train on the plan, staff for it, and have the equipment/materials needed to remove water/ice/snow as soon as possible. Assign responsibility for implementation.
- Prevent moisture from migrating through the building using manufacturer-approved methods to seal seams, joints, column bases, splines, or other interfaces.
- Incorporate technology to monitor moisture/humidity/temperature as the building is enclosed and control these factors.
- Consider coatings that are water/UV resistant and/or fire retardant.
- Institute wet works permitting simi[1]lar to hot works permitting.
- Ensure any materials installed over mass timber that subsequently become wet are removed to inspect, and allow for drying of mass timber elements.
- Implement detailed and specific QA/ QC for mass timber—ongoing QA/ QC must include proper maintenance of all the measures put in place to protect against water damage. If not maintained, a barrier meant to keep water out could easily do the opposite, leading to more damage, rather than less. Assign responsibility, create an inspection schedule, and make sure it is followed.
While all these plans may seem familiar, adapting them for use on a mass timber project is quite an effort. However, not all the work of making mass timber successful falls on builders. Insurers and industry partners are working hard to understand the performance and repairability of mass timber.
What Is the Insurance Industry Doing to Help?
One example of the work being done is the Mass Timber Insurance Action Plan (MTIAP). This is a joint initiative of the Climate Smart Buildings Alliance and the Canadian Wood Council aimed at addressing the root causes for insurance rates which may be limiting the adoption of mass timber. The project was developed over 2024 working with a network of over 25 insurance organizations as well as over 30 other timber/building organizations through a series of workshops and solutions labs looking to understand the central concerns and barriers, and potential routes to address those. It is being funded by Natural Resources Canada’s Green Construction Through Wood program.
The first phase of the MTIAP includes four pilots exploring potential solutions to persistent challenges. Each pilot is taking an agile, iterative approach to solutions development, so the outputs work for all stakeholders. The work is divided into four primary challenges:
• Challenge 1 - Limited Data Volume. The small number of mass timber insurance claims mean insurers have limited data to establish risk models. This pilot is exploring the potential of a data trust to allow organizations, either insurers or general contractors, to securely share real-world data on incidents in a way that helps everyone better understand risk and restoration implications.
• Challenge 2 - Limited Relevant Research. Most mass timber research has focused on regulatory concerns (e.g., will a mass timber fire self-extinguish). Limited research has been conducted around the concerns of insurers, for instance, whether a building’s value can be fully restored following a water/fire incident. This pilot worked to identify and rank the key research questions the insurance industry would like to see answered and proposed a set of design principles to guide researchers looking to perform research that will be relevant to the insurance industry.
• Challenge 3 - Contractor Verification. Mass timber construction is highly specialized. The skill and experience of contractors is essential to successfully delivering mass timber projects. Presently, insurers have no standard method of assessing a general contractor’s expertise and potential risk. Working with a technology firm that operates a subcontractor prequalification platform, this pilot has developed a scoring methodology that incorporates a special modifier for mass timber experience. Once live, the platform will help insurers understand a contractor’s experience and potential risks for mass timber.
• Challenge 4 – Insurance Capacity. Many insurers are only able to offer limited capacity for mass timber projects, resulting in multi-party subscriptions being the norm for larger projects. This pilot explored the potential impacts of a government- or industry-backed captive covering lower-level claims and whether this approach could help increase overall capacity across the industry. This concept is being shared with multiple government and industry groups as an innovative policy approach to help reduce development expenses for new mass timber projects.
The first phase of the MTIAP will conclude at the end of 2025 with a final report. A second phase is currently being envisioned for several of the projects above, including the development of a Mass Timber Testing and Training Facility (MT3F) to put many of the research questions identified into live tests. The project in development is proposing an in-situ, scenario-based approach to complement and validate existing in-lab fire and wetting repair assessments. This collaborative approach offers fresh hope for overcoming mass timber insurance challenges. Continued innovation and research promise to foster greater understanding, reduce risk, and support the broader adoption of mass timber—benefiting insurers, builders, and communities for years to come.