The reduced cross-section method (RCSM) is included in Eurocode 5 (EN-1995-1-2) for the design of timber members in fire conditions. The method considers the strength and stiffness reduction beneath the charred layer by adding an additional depth (known as the 'zero-strength' layer) to the charring depth. The zerostrength layer is one of the key parameters for the fire design of timber members. Recently, some concerns have been raised that the zero-strength layer might be nonconservative in some applications. This paper presents the background to the RCSM, followed by a short discussion on the mechanical assumptions, simplifications and possible limitations of the method itself. Further, it discusses determination of the zero-strength layer thickness for members in bending, tension and compression, and provides guidelines on the use of standard experimental tests to determine this quantity. For demonstration of the determination procedure, the results of fire tests in bending, tension and compression were analysed following the described procedure. Results show that the zero-strength layer exceeds the value used in practice, indicate that the method of Eurocode 5 may be non-conservative and should be revised.

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Cross-laminated timber (CLT) panels are relatively new engineered wood products that can be used as load bearing walls, floors and roof elements in innovative and high quality modern timber structures. The fire behavior of cross-laminated timber panels requires careful evaluation to allow the expansion of CLT elements usage in buildings. A University of British Columbia study has been conducted at the Trees and Timber Institute CNR-IVALSA in San Michele all'Adige, Italy to experimentally evaluate the fire performance of Canadian CLT panels. In total, ten loaded fire tests were performed using standard fire curves (ULC/ASTM and ISO) to study the influence of different cross-section layups on the fire resistance of floor and wall elements and to investigate the influence of different anchors on the fire behavior of wall elements. This paper presents the main results of the experimental analyses and discusses in particular the charring rate, one of the main parameters in fire design.