New research is challenging long-held beliefs about the amount of gypsum board needed to protect mass timber structures. Could a more nuanced, risk-based approach be adopted?. Mass Timber Fire Research: Debunking Common Encapsulation Myths New, cutting edge research is fundamentally challenging long held assumptions about the fire protection requirements for mass timber structures, particularly regarding the encapsulation of Cross Laminated Timber (CLT) and Glued Laminated Timber (glulam). This groundbreaking work suggests that current industry practices, often driven by conservative interpretations and a lack of detailed understanding of mass timber's inherent fire performance, may be leading to over specification of gypsum board and other protective layers. The findings open the door to a more nuanced, risk based approach to fire engineering design, promising not only significant cost savings and reduced environmental impact but also a more honest and efficient use of this sustainable building material. Could the UK construction sector be on the cusp of a paradigm shift in how it approaches fire safety in timber construction? Background The resurgence of mass timber in the UK, particularly CLT and glulam, is driven by its environmental credentials, speed of construction, and aesthetic appeal. However, its widespread adoption has been met with understandable caution from a fire safety perspective. Traditional perceptions of timber as a combustible material have often led to prescriptive, and arguably overly conservative, fire protection strategies. The primary method of achieving required fire resistance periods (FRPs) in mass timber structures has been through encapsulation, typically using multiple layers of gypsum plasterboard. This approach aims to protect the timber from ignition and charring for the duration of the fire, ensuring structural integrity. Current UK building regulations, notably Approved Document B (ADB), provide guidance on fire safety. While ADB doesn't explicitly detail mass timber, fire engineers typically apply principles derived from steel and concrete structures, coupled with specific timber guidance from standards like BS EN 1995 1 2 (Eurocode 5, Part 1 2: Structural fire design of timber structures). However, Eurocode 5, while foundational, is often interpreted conservatively, especially when dealing with the complex charring behaviour of mass timber. The industry has largely relied on empirical data and established charring rates, often leading to designs that incorporate significant sacrificial timber sections or extensive encapsulation. The Grenfell Tower tragedy and subsequent legislative changes, including the Building Safety Act 2022 (BSA 2022), have placed an unprecedented focus on fire safety. The BSA 2022 introduces a more stringent regulatory regime for higher risk buildings, with the Health and Safety Executive (HSE) acting as the new Building Safety Regulator. This new landscape demands robust, evidence based fire engineering solutions. For mass timber, this means a greater imperative to demonstrate intrinsic safety and justify design choices with sound scientific backing, moving beyond mere compliance to genuine safety assurance. Key Developments Recent research, conducted by leading academics and fire engineering consultancies, has delved deep into the charring behaviour and fire performance of encapsulated mass timber. This research, often involving large scale furnace testing and advanced computational modelling, is yielding surprising results. One significant finding challenges the assumption that all layers of gypsum board contribute equally to fire resistance. Studies are demonstrating that the outermost layers play a disproportionately critical role in delaying ignition and slowing the charring rate of the underlying timber. Once these outer layers fail, the subsequent layers may offer diminishing returns in terms of additional fire resistance, particularly if the fire is well developed. This suggests that simply adding more layers might not be the most efficient or effective strategy beyond a certain point. Furthermore, the research is highlighting the importance of understanding the precise charring rate of different mass timber products under various fire scenarios. It's becoming clear that generic charring rates, often used in design, may not accurately reflect the performance of specific CLT or glulam products, which can vary based on timber species, adhesive type, and manufacturing process. Some studies indicate that the charring rate can be significantly slower than previously assumed, especially when protected by even a modest amount of encapsulation. Another crucial area of investigation is the performance of connections and interfaces within mass timber structures under fire conditions. While the timber elements themselves may perform well, the integrity of connections, often made of steel, can be a weak link. The research is exploring how encapsula