The 2024 edition of the ANSI/AWC Fire Design Specification (FDS) for Wood Construction was approved as an American National Standard in September of 2023. The FDS is a design resource for the fire design of wood members, assemblies and connections and applies to fire design of wood construction within the scope of the 2024 ANSI/AWC National Design Specification (NDS) for Wood Construction. This recent edition of the FDS includes several important updates on issues like fire-resistance rating of connections between wood members, ignition-resistance requirements for exterior wood products, updates to provisions for calculating char depth, char penetration and more, as summarized below.
In 2001, provisions for calculating the fire-resistance rating of exposed wood members were added to Chapter 16 of the NDS. The model and data included in the 2001 NDS were based on the American Wood Council’s (AWC) Technical Report 10 (TR10) Calculating the Fire Resistance of Exposed Wood Members. AWC’s industry-leading research and testing led the way then and has continued to do so today. The first edition of the FDS was released in 2022 to supplement the NDS and provide additional support to architects, designers and contractors as they determine the fire-resistance ratings of wood members and assemblies. The FDS and NDS are meant to work in tandem, with the FDS providing fire design procedures that are not addressed in NDS Chapter 16.
The FDS contains three chapters, the first provides necessary scoping and definitions, the second specifies ignition and flammability requirements and references test standards, and the final chapter includes fire-resistance design provisions for wood structural members, assemblies and connections. In addition, the FDS has supplemental design information on flame-spread indices and smoke-development indices for tested wood products and fire-resistance ratings of tested wall and floor-ceiling assemblies. The 2024 FDS has several critical changes summarized below:
Chapter 1: Portions of Section 1.7, which addresses general design requirements for fire-resistance-rated wood members and assembles and provisions for the protection of connections that require a fire-resistance rating, were revised to include the newly enhanced provisions for detailing at joints and intersections. The FDS Commentary offers further details to Section 1.7 and includes diagrams that illustrate how these joints and intersections between fire-resistance-rated assemblies can be detailed to prevent premature burn-through.
Chapter 2: The ignition and flammability requirements of Chapter 2, which are coordinated with the requirements of model building codes, have been expanded to more thoroughly address requirements specific to wood materials and assemblies. Section 2.2, in particular, clarifies the requirements for ignition-resistance of wood products on exterior surfaces.
Chapter 3: FDS Chapter 3 is aligned with NDS Chapter 16 and contains design provisions for determining the fire resistance of wood construction covered under the scope of the NDS. This chapter contains procedures for calculating the structural fire resistance of both exposed and protected wood members, assemblies and connections. It also provides procedures for calculating thermal separation and burn-through times of wood assemblies. While much of the provisions in Chapter 3 will be familiar to those who have used the NDS, there is additional guidance in the FDS that offers clarification and design options related to the fire design of materials like glued-laminated timber, lumber decking and cross laminated timber.
The 2024 FDS provides a new design resource that supplements the NDS to offer further clarity, detailing and provisions for fire design of wood construction. In addition to containing provisions consistent with NDS Chapter 16, the 2024 FDS provides new fire design calculation procedures related to protected wood members and assemblies. The 2024 FDS is accessible for free on the AWC website at https://bit.ly/3XR0Nba and the 2024 NDS is available to view at https://awc.org/publications/2024-nds/. FBN
