TCC floors offer sustainability and structural benefits, but how do they perform in a fire? Analyse recent large-scale fire test data on the integrity and insulation of TCC systems with CLT panels.. The Rise of Timber Concrete Composite (TCC) Structures in Sustainable Construction The construction industry is continually seeking innovative solutions to reduce its environmental impact. Timber Concrete Composite (TCC) floor systems have emerged as a promising answer, combining the sustainability and aesthetic appeal of timber, often in the form of Cross Laminated Timber (CLT), with the structural robustness and thermal mass of concrete. This hybrid approach offers significant benefits, including a lower carbon footprint compared to traditional reinforced concrete structures, faster construction times, and enhanced acoustic performance. As architects and engineers increasingly specify these materials for a wide range of buildings, from residential blocks to commercial spaces, understanding their performance under extreme conditions, particularly fire, becomes paramount. This article delves into crucial new research from late 2026, providing vital insights into the fire resistance of TCC floor systems. Navigating the Regulatory Landscape: Fire Safety in Modern Construction The regulatory framework governing fire safety in the UK is stringent and continually evolving. The Building Safety Act 2022 (BSA 2022) places a heightened emphasis on the safety of higher risk buildings throughout their lifecycle, placing clear responsibilities on Accountable Persons and Principal Designers. This is further complemented by the Regulatory Reform (Fire Safety) Order 2005 (RRO 2005), which mandates that Responsible Persons conduct comprehensive fire risk assessments and implement appropriate fire precautions. For TCC systems, compliance with Approved Document B (ADB) of the Building Regulations concerning fire safety, as well as relevant British Standards like BS 9991 (Fire safety in the design, management and use of residential buildings) and BS 9999 (Fire safety in the design, management and use of commercial buildings), is critical. The forthcoming research directly informs how such systems can meet these onerous requirements. The Challenge of Fire and Hybrid Structures While the sustainability credentials of mass timber, including CLT, are undeniable, public perception and historical precedent often raise concerns about its fire performance. While timber chars predictably, protecting the inner core, the introduction of a composite concrete layer in TCC systems alters this dynamic significantly. The interface between the two materials, the behaviour of the connection mechanisms, and the potential for delamination under thermal stress are all critical factors that require thorough investigation. Traditional fire testing methods for single materials may not fully capture the complex interactions within a composite system. This new research directly addresses these complexities through large scale fire testing, offering a more realistic understanding of how TCC floors will behave in a real fire scenario, particularly concerning integrity and insulation. New Large Scale Fire Testing: Unveiling TCC Performance A significant body of new research, published in late 2026, presents the results of large scale fire tests on TCC floor systems utilising CLT panels. These tests provide invaluable data on the fire resistance, specifically focusing on integrity and insulation. Integral to fire safety, 'integrity' refers to the ability of a fire resisting element to prevent the passage of flame and hot gases, whilst 'insulation' refers to its ability to restrict the temperature rise on the unexposed side. The research rigorously simulated fire conditions specified in relevant standards, carefully monitoring temperature profiles, deflection, and the onset of failure criteria. Initial indications suggest that well designed TCC systems, with appropriate concrete cover and connection details, can achieve impressive fire resistance periods, potentially exceeding common regulatory requirements when properly engineered. Key Findings: Integrity and Insulation in Focus The large scale fire tests have provided critical data points for both the integrity and insulation performance of TCC floors. For integrity, the tests examined how effectively the composite system prevented the passage of flames and hot gases. The results indicated that the concrete topping played a crucial role in protecting the CLT from direct flame impingement and in maintaining compartmentalisation. Regarding insulation, the research focused on the temperature rise on the unexposed surface of the floor. The combination of the concrete's thermal mass and the charring layer of the CLT contributed to effective thermal insulation, delaying the temperature increase to levels that would compromise adjacent compartments or escape routes. These findings are vital for fire engineers undert